l'ans

Ans is the plural of an (year), and one of the highest-frequency noun forms in spoken French because of how often it appears in two everyday constructions: ages and durations. French does not say "I am twenty-five years old" with the verb être; you say j'ai vingt-cinq ans (literally "I have twenty-five years"). That single idiom is responsible for a huge chunk of ans usage.

The second main use is for durations counted in whole years: depuis cinq ans (for five years, ongoing), il y a dix ans (ten years ago), dans deux ans (in two years). When the focus shifts to a year as a lived stretch with qualities ("a good year", "this year"), French uses année instead: une bonne année, cette année-là. The pronunciation of ans in liaison contexts is /ɑ̃z/, so deux ans sounds like deu-zan. See the an word page for the singular form and the full an vs année distinction.