Sustain, v. t. [imp. & p. p. Sustained; p. pr. & vb. n. Sustaining.]
Etymology: [OE. sustenen, susteinen, OF. sustenir, sostenir, F. soutenir (the French prefix is properly fr. L. subtus below, fr. sub under), L. sustinere; pref. sus- (see Sub-) + tenere to hold. See Tenable, and cf. Sustenance.]
1. To keep from falling; to bear; to uphold; to support; as, a foundation sustains the superstructure; a beast sustains a load; a rope sustains a weight. Every pillar the temple to sustain. Chaucer.
2. Hence, to keep from sinking, as in despondence, or the like; to support. No comfortable expectations of another life to sustain him under the evils in this world. Tillotson.
3. To maintain; to keep alive; to support; to subsist; to nourish; as, provisions to sustain an army.
4. To aid, comfort, or relieve; to vindicate. Shak. His sons, who seek the tyrant to sustain. Dryden.
5 more senses
5. To endure without failing or yielding; to bear up under; as, to sustain defeat and disappointment.
6. To suffer; to bear; to undergo. Shall Turnus, then, such endless toil sustain Dryden. You shall sustain more new disgraces. Shak.
7. To allow the prosecution of; to admit as valid; to sanction; to continue; not to dismiss or abate; as, the court sustained the action or suit.
8. To prove; to establish by evidence; to corroborate or confirm; to be conclusive of; as, to sustain a charge, an accusation, or a proposition.
Syn. -- To support; uphold; subsist; assist; relieve; suffer; undergo.
1 other Webster entry under this spelling
Sustain, n.
One who, or that which, upholds or sustains; a sustainer. [Obs.] I waked again, for my sustain was the Lord. Milton.
Shades of meaning
Fernald has no entry of its own for sustain; he lists it under carry, confirm, endure, help, keep, support.
Where he writes about it:
Support and sustain alike signify to hold up or keep up, to prevent from falling or sinking; but sustain has a special sense of continuous exertion or of great strength continuously exerted, as when we speak of sustained endeavor or a sustained note; a flower is supported by the stem or a temple-roof by arches; the foundations of a great building sustain an enormous pressure; to sustain life implies a greater exigency and need than to support life; to say one is sustained under affliction is to say more both of the severity of the trial and the completeness of the upholding than if we say he is supported. — from support