1. Legally obligated or responsible: liable to pay for damages; liable for negligence. See Synonyms at responsible.
2. Subject to undergoing or suffering something, especially something unpleasant. Used with to: We did not use glass containers because they are liable to breakage.
3. Likely. Often used with reference to an unfavorable outcome: People who are sleep deprived are liable to make mistakes.
[Middle English, probably from Old French lier, to bind, from Latin ligāre; see leig- in the Appendix of Indo-European roots.]
Usage Note: Liable, apt, and likely are used interchangeably in constructions with infinitives, as in Zach is liable to lose, Zach is apt to lose, and Zach is likely to lose, but the three words have subtle distinctions in meaning. A traditional rule holds that liable should be used only if the subject would be adversely affected by the outcome expressed by the infinitive. The rule therefore permits Tim is liable to fall out of his chair if he doesn't sit up straight but not The chair is liable to be slippery, though constructions of the latter type have long been common in reputable writing. · Apt usually suggests that the subject has a natural tendency enhancing the probability of an outcome and that the speaker is somewhat apprehensive about the outcome. Thus apt is more naturally used in a sentence like The fuel pump is apt to give out at any minute than in Even the clearest instructions are apt to be misinterpreted by those idiots (since the instructions are not at fault) or in The fuel pump is apt to give you no problems for the life of the car (since there is no reason that the speaker should regard such an outcome as unfortunate). · Likely is more general than either liable or apt. It ascribes no particular property to the subject that would enhance the probability of the outcome. Thus, while John is apt to lose the election may suggest that the loss will result from something John does or fails to do, John is likely to lose the election does not. Nor does it suggest anything about the desirability of the outcome from the point of view of either the speaker or the subject.
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