synthesis

The general sense, and the one closest to the Greek: súnthesis, "a putting together," built from sun- "together" and títhēmi "set, place." English sandhi is its doublet, the same source reaching English by another road. The ingredients follow of, as in a synthesis of different art forms. The noun is countable or not, and its plural is syntheses.

The chemist's working noun. A synthesis is usually a planned route to a target compound, run as a single step or a sequence of them, and judged by yield, selectivity and purity. It is freely countable (a three-step synthesis). The product follows of and the starting materials follow from: the synthesis of ammonia from nitrogen and hydrogen.

Signal processing uses the word for building a signal up rather than breaking one down. In additive synthesis, sine waves of differing frequency, amplitude and phase are summed, an idea formalized by Fourier theory. In practice the word rarely stands alone. A modifier usually names the technique, as in additive synthesis or granular synthesis, and that phrase is how engineers and sound designers talk about it.

Here synthesis is the third moment of a dialectic, tied above all to Hegel. It reconciles a thesis with its antithesis and keeps something of each in a higher, unified concept. The three words travel as a set, and this sense rarely appears without the other two nearby. Unlike the logician's deduction, nothing is derived; a contradiction is overcome.

Logic defines synthesis against analysis. Analysis works backward from the proposition to be proved, while synthesis moves forward from accepted premises or axioms to the particular conclusion. Classical geometry favored this forward method. Keep it apart from the dialectical sense, where a synthesis resolves a conflict instead of following from a premise.

Grammar uses synthesis for the work of fusing separate ideas into one sentence. The writer decides which ideas to coordinate and which to subordinate, so that the relationships among them show in the syntax. When two short statements become a single complex sentence, that combining is synthesis.

Intelligence work treats synthesis as one stage in a cycle. Raw material is first processed. It is then combined with other collected information and finished intelligence into an all-source picture that supports decisions. The emphasis falls on fitting many sources together rather than on judging any single one, which is why the word suits briefings and assessments for commanders.

Surgery keeps the Greek "putting together" at its most literal. It means rejoining fractured bone or severed tissue so that the anatomy is continuous again. The sense survives most visibly in compounds such as osteosynthesis, the surgical rejoining of broken bone. There the word describes restoring what was already whole, not making something new.

A rhetorician's term for how the pieces of a text are fitted together. It covers word choice, clause length and sound, chosen for euphony and rhythm rather than for sense alone. It names a craft of arrangement, so it is something a stylist is praised for and a translator tries to keep. The grammatical sense joins ideas into a sentence; this one is about how the result sounds.

A garment, not an idea: the dinner dress Romans changed into. It was informal enough that, according to the American Philological Association's Transactions of 1918, the Saturnalia was apparently the only occasion when it could be worn in public with decorum. As with the other senses, the plural is syntheses.