One who others.

People of the past thought and acted differently.

One's romantic partner, regardless of marital status or gender. / A person with whom one has an important bond of some kind.

(sequence, idiomatic) From another point of view.

(informal) A woman who is romantically involved with someone (usually a man) already in a committed relationship with another woman, especially a woman having an affair with a married man.

(British) A formulaic name that is substituted for that of a person whose name or identity is not known, or not relevant; typically used when exhibiting an example.

All except for some previously mentioned set. / Every second/two; each alternate; the second of each pair in turn.

(reciprocal pronoun) To one another; one to the other; signifies that a verb applies to two or more entities both as subjects and as direct objects:

(euphemistic) Hell

Something unspecified or indeterminate, or whose name is forgotten or immaterial.