ALTERNATE a. 2 definitions
Designating the members in a series, which regularly intervene between the members of another series, as the odd or even numbers of the numerals; every other; every second; as, the alternate members 1, 3, 5, 7, etc. ; read every alternate line.
AN n.
y called the indefinite article. It is used before nouns of the singular number only, and signifies one, or any, but somewhat less emphatically. In such expressions as "twice an hour," "once an age," a shilling an ounce (see 2d A, 2), it has a distributive force, and is equivalent to each, every.