constraint
Pluralconstraints
- 1A restriction or limitation that holds something within certain bounds.
Budget constraints forced the team to cut several features.
The new policy placed a constraint on how much water each household could use.
Similarrestriction, limitation, limit, restraint, check
Note
The general sense, and the one the others specialize: Middle English constreynt, from Old French constreinte, ultimately from Latin cōnstringō, whose past participle cōnstrictus will look familiar. A constraint is something you work within, not something you remove. An engineer eliminates a problem but designs around a constraint. In the plural it is everyday planning language, as in budget constraints or constraints that may occur in the long run.
- 2An irresistible force or compulsion that drives a person to act.
A strange constraint drove him to confess everything that night.
She acted under a constraint she could neither name nor resist.
Similarcompulsion, force, pressure, duress
Note
Here the force pushes rather than holds back. Where the restricting sense fences action in, this one drives it. It sits naturally in the phrase under constraint, often sharpened by an adjective (they confessed only under severe constraint). Used this way, it names pressure a person cannot resist and usually implies that what followed was not freely chosen.
- 3The act of holding back or hiding one's true feelings.
He answered with obvious constraint, keeping his real opinion hidden.
The constraint in her voice told everyone she was upset.
Similarrestraint, reserve, reticence, inhibition, stiffness
Note
Restraint turned inward, on one's own feelings. Charles Dickens, in Barnaby Rudge (1841), describes a man whose wrath could have struck his enemy dead, yet who "put such fierce constraint upon himself" that he passed without a word or look. The construction to know is put constraint upon oneself. The noun can also name the stiffness that restraint leaves behind in a voice or a manner.
- 4In optimization, a condition that any acceptable solution to a problem must meet.
The optimization model included a constraint limiting total cost to the available budget.
Adding a single constraint can shrink the set of feasible solutions dramatically.
Similarrestriction, condition
Note
Mathematicians usually write it as an equation or inequality. Taken together, the constraints mark out the feasible region, and only points that satisfy every one of them qualify as candidate solutions. Adding a single constraint can shrink that region sharply. Keep it distinct from the quantity being optimized: a constraint decides what is allowed, not what is best.
- 5A linkage or other restriction that maintains the integrity of data stored in a database.
A foreign key constraint links each order to a valid customer record.
The developer added a constraint to prevent duplicate entries in the table.
Note
In database work it is a declarative rule that the system itself enforces. It states which values or relationships the stored data may have, and any operation that would break the rule is rejected rather than allowed through. A foreign key constraint is the classic linkage, tying each record to a valid record elsewhere. Other constraints guard against duplicates or missing values.
Practice
Can you tell the meanings of constraint apart? Answer 3 quick questions from this page, or write your own sentence and AI will check it.
Origin
The word comes from Middle English constreynt, from Old French constreinte, the past participle of constreindre ("to constrain"), which came from Latin cōnstringō (linked to the past participle cōnstrictus).