When do you use an and when do you use année to say "year" in French?
As you are probably aware, French has two words for year: the masculine word an and the feminine word année. Choosing between these apparent alternatives is a common question for beginners (and indeed even more advanced students). So, when do you use an and when do you use année?
The basic difference between the two words has to do with how you "view" the year in a particular case. As a rough guide:
In practice, this means that we can identify some common conditions that mean that an or année is used in a given case. These common conditions are summarised in the following table.
As you will appreciate, not every single case is clear-cut. Given that an has a "counting" function, while année tends to "describe" or "focus on an experience", there are cases where either is potentially possible: whether you say j'y ai consacrée dans ans de ma vie ("I dedicated two years of my life to it") or ...deux années de ma vie depends on whether you wish to place more emphasis on the "counting the length of time" or on the "experience" of those two years.
Warning for literature students
For those students who are into their 19th century classics in particular, it is worth noting that the usage of an vs année has changed over time, including some changes in the relatively recent history of the language. Thus, up until the 19th century at least, it was common to use ans with quantifiers and ordinal numbers, whereas annéees is almost always used in such cases today. (In older literature, you will also find ans used readily with other determiners and adjectives: "en mes ans", "mes vieux ans" etc.) So if you are used to reading phrases such as "tout l'an", "les premiers ans de ma vie" etc in literature, be aware that nowadays people would generally say toute l'année, les premières années etc.