# Use of the Article

Which one is a correct use of the Article in the following two sentences?

1. A leap year is a year with an extra day. (a year)
2. A leap year is the year with an extra day. (the year)
• In this case, either might be correct, depending upon context. If one were describing, to someone unfamiliar with the Gregorian calendar, how a leap year differs from a non-leap year, she might well use the second form. . . . . . Questions about use of the articles may be the most common of all at ELL. – P. E. Dant Reinstate Monica Jun 10 '17 at 3:43
• Eh, I don't think the indefinite would be very likely followed by the definite in this sentence. Only the first is really correct. In any case, unless defining something of which there is only one, the indefinite is more normal. – Luke Sawczak Jun 10 '17 at 4:32
• There is no point in following an indefinite with a definite in an intransitive statement. – user3169 Jun 10 '17 at 4:52

Absent a context that requires you to be singling out a specific leap year from other non-leap years, normal idiomatic usage when offering a definition is to use the indefinite article:

A leap year is a year with an extra day.

The indefinite article there is a form of generalization. The use refers to the noun as exemplar.

An example where you have to single out which year is the leap year:

Identify the leap year:

2000 2001 2002 2003

Which article to use depends on whether the noun it goes with is a specific instance of it that has already been introduced. I'm having trouble thinking of a context where you would have introduced a particular year, without also introducing the concept of a leap year.

Your first sentence is the typical way to explain what a leap year is. This would be a way to correctly use the definite article:

In any series of four years, there is always one leap year. The leap year is the year with an extra day.

As you can see, we have already introduced a specific leap year, as well as a specific set of years. So we would use the in both cases.