boyfriend
The French term 'petit ami' is used to refer to a boyfriend. Like in English, it can colloquially refer to a male companion or partner in a romantic or sexual relationship. It is commonly used in both formal and informal settings.
My boyfriend is very nice.
This sentence is an example of a simple positive statement. In this case, 'petit ami' is being used to refer to the speaker's boyfriend and 'est très gentil' describes him as very nice.
I am going to the cinema with my boyfriend.
This is an example of a future action, indicated by the phrase 'vais au', which means 'am going to'. The speaker is saying they plan to go to the cinema with their boyfriend, who is referred to as 'petit ami'.
This is Marie's boyfriend.
In this instance, 'petit ami' is used to describe the relationship between a person (in this case, Marie) and their boyfriend. Marie's ownership of the boyfriend is indicated by 'de', which translates to 'of'. Taken together, the phrase reads 'This is the boyfriend of Marie' or, more naturally in English, 'This is Marie's boyfriend'.