Example:—Homer, the greatest poet of antiquity, is said to have been blind.
Words or phrases contrasted with each other, or having a mutual relation to others that follow them in the same clause, are separated by commas.
Example:—False delicacy is affectation, not politeness.
A comma is put before a relative clause when it is explanatory of the antecedent or presents an additional thought.
Example:—Behold the emblem of thy state in flowers, which bloom and die.
But the point is omitted before a relative that restricts the general notion of the antecedent to a particular sense.
Example:—Every teacher must love a boy who is attentive and docile.
Expressions of a parenthetical or intermediate nature are separated from the context by commas.
Example:—The sun, with all its attendant planets, is but a very little part of the grand machine of the universe.