The pacification or putting down of unruly forces is suggested by all these words. Subdue is the mildest of the group, implying a gentle but firm force exerted to moderate an impulse that might otherwise be dangerous: subduing his momentary impulse to tell his boss what he thought of him. Subdue implies that the threatening force has been put down but not necessarily altered or diminished in any basic way. Inhibit , consequently, goes further than subdue in suggesting a fundamental altering of the rebellious impulse; this is achieved, by implication, through blocking its chances for growth or decreasing the area within which it can continue operating effectively. The word often refers disapprovingly to the diminishing of natural or healthy instincts: excise laws that would fatally inhibit free trade; over-restrictive or over-permissive parents who inhibit the normal maturation of their children.

A similar relationship exists between check and curb . Like inhibit, check involves the prevention of further growth; curb , on the other hand, suggests the moderating force implicit in subdue : merely wishing to curb some thoughtless tendencies in her pupils, while checking altogether any tendency towards outright hostile acts. Check is stronger than inhibit in sometimes implying the complete rooting out of an impulse. Similarly, curb is much stronger than subdue in suggesting the use of considerable force, when necessary, in order to counter any threatened unruliness. Because it suggests difficulty and struggle, in fact, curb has greater force than check , even though the latter points to the complete extirpation of an impulse: A few concessions wisely made would have completely checked the revolution; now whole armies thrown into the breach may not be sufficient to curb it.

Repress and suppress , besides sounding so similar, are often used almost as though they were different spellings of the same word. They are differently defined by psychologists, and even in ordinary use a contrast in meaning can be observed. In psychology, repress indicates a process of returning to the unconscious mind fears and impulses so that they cannot be easily called up again; this process occurs without the subject’s knowledge. Suppress , in contrast, relates to a single effort of will in putting away an unpleasant thought; this act may or may not be conscious, and the suppressed idea can more easily be recalled for consideration. The ordinary uses of these two words reflect a similar comparison; repress is felt as the stronger here, often implying a harsh or excessive stamping out of dissent or rebellion. Except for its greater force, it is thus similar to check and inhibit . Suppress suggests bringing something under control, like subdue and curb , although it suggests the use of greater force than either.

Constrain and restrain makes a comparable pair, but they are much more clearly distinguished in common use than repress and suppress . Constrain indicates forcing someone else to do something against his will and carries an overtone of disapproval for such an act: constraining his daughter from going out with boy-friends. Restrain suggests a gentler, advisory moderation and may sometimes refer to a self-imposed discipline. As such, it can often be used with a tone of approval: restraining himself from drinking to excess.