sight

Concise Oxford English Dictionary © 2008 Oxford University Press:
sight/sʌɪt/

▶noun

• 1 the faculty or power of seeing.

• 2 the action or fact of seeing someone or something.

  ■ the area or distance within which someone can see or something can be seen.

• 3 a thing that one sees or that can be seen.

  ■ (sights) places of interest to tourists and other visitors.

• 4 (a sight) informal a person or thing having a ridiculous or unattractive appearance.

• 5 (also sights) a device on a gun or optical instrument used for assisting in precise aim or observation.

▶verb

• 1 manage to see or briefly observe.

• 2 take aim by looking through the sights of a gun.

• 3 take a detailed visual measurement with or as with a sight.

  ■ adjust the sight of (a gun or optical instrument).

– phrases
at first sight when first seen; from an initial impression.
in sight

• 1 visible.

• 2 close to being achieved or realized.

in (or within) sight of

• 1 so as to see or be seen from.

• 2 within reach of; close to attaining.

in (or within) one's sights

• 1 visible, especially through the sights of one's gun.

• 2 within the scope of one's ambitions or expectations.

lose sight of

• 1 be no longer able to see.

• 2 fail to consider, be aware of, or remember.

on (or at) sight as soon as someone or something has been seen.
out of sight

• 1 not visible.

• 2 (also outasight) informal extremely good; excellent.

raise (or lower) one's sights become more (or less) ambitious; increase (or lower) one's expectations.
set one's sights on hope strongly to achieve or reach.
a sight —— informal indicating considerable extent: she is a sight cleverer than Sarah.
a sight for sore eyes informal a person or thing that one is extremely pleased or relieved to see.
a sight to behold a person or thing that is particularly impressive.

– derivatives
sighted adjective,
sighter noun,
sighting noun.

– origin OE (ge)sihth ‘something seen’, of W. Gmc origin.

usage: On the confusion of sight and site, see usage at site.