radical

Less common meanings

10. 10
    math rootnouncountable

    A root of a number or quantity, such as a square root or cube root; also the root sign √, or an expression written with it.

    Simplify the radical before adding it to the other terms.

    A radical can be rewritten as a number raised to a fractional power.

    Similarroot, surd

    Note

    In school arithmetic the word names the root, and loosely the whole expression including the √ sign. Textbooks tell you to simplify the radical, or to add radicals with the same index. The small index beside the sign gives the degree of the root, and when no index is written, a square root is meant. For the sign and the adjective, see the mathematical adjective. Source

    Checked 31 Oct 2026 · 4 facts

    • The expression under the sign is the radicand; the whole expression including the sign is a radical expression. openstax.org
    • Textbooks instruct learners to simplify radicals and add radicals with matching indices. openstax.org
    • The index specifies the degree of the root. openstax.org
    • An omitted index means a square root. spot.pcc.edu
11. 11
    awesomeadjectivedated

    Excellent or very impressive; an enthusiastic term of approval.

    The whole road trip turned out to be absolutely radical.

    Everyone agreed the new ramp at the park was radical.

    UsageNow sounds dated or playfully retro; outside fiction and jokes, awesome or excellent is safer.

    Similarrad

    Oppositelame, boring

    Note

    Slang of the 1980s and 1990s, used as all-purpose praise for a stunt, a song or a party, and often clipped to rad. Because the word belongs so firmly to that era, it now sounds dated or knowingly retro, and in fiction it can fix a character's period voice. Source

    Checked 3 Nov 2026 · 3 facts

    • The approving slang belongs to the 1980s and 1990s; no claim of first use is made. mambo-world.com.au
    • Radical serves as general praise, including for a stunt; the song and party are illustrative applications. en.wiktionary.org
    • Rad is a clipping of radical in its approving sense. en.wiktionary.org
12. 12
    atom groupnoundatedcountable

    In chemistry, a set of covalently bonded atoms that behaves as one unit in reactions.

    In many salts, an acid radical combines with a metal ion.

    The ammonium radical behaves as a single charged unit in solution.

    Similargroup

    Note

    In older chemistry, and still in some school textbooks, the word names a bonded cluster that behaves like a single atom, such as the ammonium radical or an acid radical in a salt. Chemists now call it a group. It can pass from one compound to another without coming apart. It shares its name with the free radical, which is typically reactive because of an unpaired electron. Context usually decides: salts and acids suggest the stable group, reaction mechanisms the free radical. Source

    Checked 1 Nov 2026 · 6 facts

    • Older chemistry described radicals as clusters of atoms behaving like elements through reactions. oyc.yale.edu
    • School chemistry materials retain the terms ammonium radical and acid radical. scert.delhi.gov.in
    • Acid radicals in salts are anions. scert.delhi.gov.in
    • Such clusters can pass intact between compounds, but they do not invariably remain intact during reactions: ammonium, for example, loses a proton to form ammonia. en.wikipedia.org
    • The older bound-group sense and the free-radical sense share the same term. iupac.qmul.ac.uk
    • Free radicals have unpaired electrons, which typically make them reactive. en.wikipedia.org
13. 13
    adjective

    In mathematics, having to do with a root or radix.

    The expression is written in radical form rather than as a decimal.

    The radical symbol indicates which root to take.

    Note

    The mathematical adjective lives mostly in fixed phrases: the radical sign √, a radical quantity, an expression left in radical form. Radix is the Latin word for 'root', so a radical expression keeps the root written out instead of working it into a decimal. The root itself, as a noun, is the arithmetic noun. Source

    Checked 31 Oct 2026 · 3 facts

    • Latin radix means root. en.wiktionary.org
    • Radical form represents a root symbolically rather than evaluating it as a decimal. spot.pcc.edu
    • The arithmetic noun radical can mean a root. en.wiktionary.org
14. 14
    word rootadjective

    Relating to the root of a word, the base form from which other forms derive.

    The radical element of the verb remains unchanged across its conjugations.

    Comparative philologists trace the radical components shared by related languages.

    Note

    Word scholars turn the plant image onto vocabulary. The radical part of a word is its root, the core left once prefixes and endings come away, and it usually stays recognizable across the word's forms. Like the other technical adjectives, it classifies and is not graded. For the separate root consonants of a Semitic word, English uses the Semitic grammar noun. Source

    Checked 31 Oct 2026 · 3 facts

    • A word's root is its basic core, without affixes. ecampusontario.pressbooks.pub
    • A root can have different forms, called allomorphs; examples include ring, rang and rung. ecampusontario.pressbooks.pub
    • The noun radical denotes an individual consonant of a Semitic root. en.wiktionary.org
15. 15
    root consonantnouncountable

    In Semitic languages, any of the consonants, typically three, that together make up a word's root.

    Linguists identify each radical by its position in the consonantal root.

    The verb's three radicals recur across all of its derived forms.

    Note

    In Semitic grammar a root is a skeleton of consonants, usually three, and each consonant is a radical. Linguists refer to them by position: first, second and third radical. Vowel patterns and affixes slot in around them to build many related words. Compare the word-root adjective, which treats the root as a single unit rather than as separate consonants. Source

    Checked 31 Oct 2026 · 4 facts

    • Semitic roots generally consist of three consonants. faculty.washington.edu
    • Each consonant of the root is a radical. faculty.washington.edu
    • Radicals are identified by their positions in the root. aqa.org.uk
    • This describes a major word-formation process, but the universal claim is too strong: some related words are derived from existing words rather than directly from consonantal roots. roa.rutgers.edu
16. 16
    adjective

    Of a plant part, arising directly from the root or the base of the stem.

    The dandelion's radical leaves form a rosette at ground level.

    Botanists described the radical buds emerging from below the soil surface.

    Similarbasal

    Note

    Botany uses the word closest to its Latin root. Radical leaves, buds or stalks spring from the base of the plant, often in a rosette at ground level, rather than from higher up the stem. The adjective classifies and does not compare: a leaf is radical or it is not, never more radical. In everyday descriptions, basal covers the same position. Source

    Checked 31 Oct 2026 · 3 facts

    • The botanical sense preserves the literal root-related meaning of Latin rādīcālis. en.wiktionary.org
    • Radical plant parts arise from the root or stem base rather than higher on the stem. en.wikipedia.org
    • Radical leaves can form a rosette near ground level. plantnet.rbgsyd.nsw.gov.au
17. 17
    prime productnouncountable

    In number theory, the product of the distinct prime factors of a positive integer.

    The radical of 360 equals 30, the product of 2, 3, and 5.

    Repeated prime factors are counted only once when computing the radical.

    Note

    Number theory uses the word for an integer with its repeated factors squeezed out. For example, 72 = 2³·3², and its radical is 2·3 = 6. Exponents are ignored, so a number and its radical share exactly the same primes, and a number with no repeated prime factor equals its own radical. The idea plays a central role in the abc conjecture. Source

    Checked 31 Oct 2026 · 5 facts

    • An integer's radical retains one copy of each prime factor, removing repetitions. cims.nyu.edu
    • 72 = 2³·3² and rad(72) = 2·3 = 6; the factorization and multiplication are verified by arithmetic. sites.math.rutgers.edu
    • Ignoring prime-factor multiplicities preserves exactly the same prime divisors; this follows directly from the definition. people.math.harvard.edu
    • A positive integer without repeated prime factors equals its radical. en.wikipedia.org
    • The radical is central to the statement of the abc conjecture. en.wikipedia.org
18. 18
    tongue-base soundadjective

    Of a speech sound, articulated using the root of the tongue, near the pharynx.

    Phoneticians classify several Arabic consonants as radical sounds.

    The radical articulation involves drawing the tongue root toward the pharyngeal wall.

    Note

    Phonetics borrows the anatomical root. A radical sound is made by drawing the root of the tongue back toward the throat. The term groups a region of articulation rather than naming a single place, and it covers both pharyngeal and epiglottal consonants. It applies only to sounds, as in radical consonants or radical articulation, and it never takes more or most. Source

    Checked 31 Oct 2026 · 3 facts

    • The phonetic meaning refers to the anatomical root of the tongue. en.wiktionary.org
    • Radical articulation involves retracting the tongue root toward the throat. phonetik.uni-muenchen.de
    • Radical can group pharyngeal and epiglottal consonants rather than designate one narrowly defined place of articulation. en.wikipedia.org
19. 19
    Celtic base formnouncountable

    In Celtic languages, the basic underlying form of an initial consonant, before the Celtic initial consonant mutations alter it.

    Welsh dictionaries list nouns under their radical, not their mutated forms.

    The radical resurfaces once the grammatical trigger for mutation is removed.

    Note

    Celtic grammar uses the word for the unmutated consonant. In Welsh and its relatives, the first sound of a word can soften, nasalize or otherwise shift after certain triggering words. The radical is the form before any of that happens. Dictionaries file words under their radical, so a learner who meets a mutated form must work back to it before looking the word up. Source

    Checked 31 Oct 2026 · 6 facts

    • The radical is the initial consonant before mutation. users.aber.ac.uk
    • Welsh initial sounds can change under the influence of preceding words. users.aber.ac.uk
    • Welsh mutations include soft, nasal and other changes. users.aber.ac.uk
    • Related Celtic languages also have initial mutations triggered by grammatical words. en.wikipedia.org
    • The radical is the form before mutation. users.aber.ac.uk
    • Dictionary entries use radical forms, requiring learners to identify the underlying form when consulting them. en.wiktionary.org
20. 20
    root idealnouncountable

    In abstract algebra, any of several related ideals or submodules, such as the radical of an ideal or of a ring or module, built from elements regarded as degenerate.

    The radical of the ideal generated by 4 in the integers is the ideal generated by 2.

    Taking the radical twice yields the same ideal as taking it once.

    Note

    Commutative algebra uses the word for an ideal that gathers in every element some power of which falls into the original ideal. Written Rad(I) or √I, it borrows the root sign because the definition works like root extraction: x belongs if xⁿ does. Taking it twice changes nothing. It is also the meeting point of all the prime ideals that contain I. Source

    Checked 31 Oct 2026 · 5 facts

    • The radical of an ideal consists of elements whose positive integer powers belong to that ideal. ms.uky.edu
    • The notation is Rad(I) or √I. en.wikipedia.org
    • The root notation reflects taking roots of elements of the original ideal. en.wikipedia.org
    • Taking the radical twice gives the same result as taking it once. math.columbia.edu
    • The radical is the intersection of all prime ideals containing the original ideal. math.ucla.edu