- unassisted (adj.)
[unassisted 词源字典] - 1610s, from un- (1) "not" + past participle of assist (v.). Related: Unassistedly.[unassisted etymology, unassisted origin, 英语词源]
- unassuming (adj.)
- "unpretentious, modest," 1726, from un- (1) "not" + present participle of assume (v.). Related: Unassumingly.
- unattached (adj.)
- late 15c., "not arrested or seized," from un- (1) "not" + past participle of attach (v.). Meaning "not associated with any body or institution" is recorded from 1796; sense of "single, not engaged or married" is first attested 1874.
- unattainable (adj.)
- 1660s, from un- (1) "not" + attainable.
- unattended (adj.)
- c. 1600, "alone, unaccompanied," from un- (1) "not" + past participle of attend (v.). Meaning "with no one in attendance" is from 1796.
- unattested (adj.)
- 1660s, from un- (1) "not" + past participle of attest (v.).
- unattractive (adj.)
- 1729, from un- (1) "not" + attractive. Related: Unattractively; unattractiveness.
- unauthorized (adj.)
- 1590s, from un- (1) "not" + past participle of authorize (v.).
- unavailability (n.)
- 1855, from un- (2) "opposite of" + availability, or else from unavailable + -ity.
- unavailable (adj.)
- 1540s, "ineffectual," from un- (1) "not" + available. Meaning "incapable of being used" is recorded from 1855. Unavailing has taken up the older sense of the word.
- unavailing (adj.)
- "ineffectual, useless," 1660s, from un- (1) "not" + availing. Also see unavailable.
- unavoidable (adj.)
- mid-15c., from un- (1) "not" + avoidable. Related: Unavoidably.
- unaware (adj.)
- 1590a; see unawares.
- unawares (adv.)
- 1530s, "without being aware," from un- (1) "not" + aware + adverbial genitive -s. Meaning "without being noticed" is recorded from 1660s. Form unaware is recorded from 1590s.
- unbalance (v.)
- 1856, from un- (2) "reverse, opposite of" + balance (v.).
- unbalanced (adj.)
- 1640s, from un- (1) "not" + past participle of balance (v.). Earliest use is in reference to the mind, judgment, etc. Of material things, it is recorded from 1732.
- unbar (v.)
- late 14c., from un- (2) "reverse, opposite of" + bar (v.). Related: Unbarred; unbarring.
- unbearable (adj.)
- mid-15c., from un- (1) "not" + bearable. Related: Unbearably. Old English had unberendlic.
- unbeatable (adj.)
- 1897, from un- (1) "not" + beatable.
- unbeaten (adj.)
- late 13c., "not beaten or struck," from un- (1) + beaten. In the sense of "undefeated" it is first recorded 1757. Old English had ungebeaten "unwrought, unstruck."
