Here are thousands of instances of "our life is short", and I seriously doubt many of them are specific to the lives of, say, a couple living together. It's perfectly normal to refer to human lives collectively in the singular. When to use "lives" as a plural of life?

Understanding the Context

- English Language & Usage ... A plural subject requires a plural object (lives), accordingly a singular subject requires a singular object (life). They can be used to mean one person or several people, however. So, if your intention is to refer to an individual who lost his or her life whilst saving the lives of more than one others, then the second is correct and the first incorrect.

Key Insights

They is singular in this context, so ... I would say still life has undergone reification, which transforms it into a "standalone word". How the subcomponent elements work grammatically doesn't automatically affect how the composite form works. Effectively it's a kind of neologism - not really "new" today, but a lot later than the original word life with its irregular plural. Neologisms almost always have regular plural and verb forms.

Final Thoughts

Why is the plural form of "life" "lives", while the plural form of ... For sentence one: Look at it like this, 'He loves his life' and 'She loves her life' are obviously correct. Now, when we we say 'People love their _ .', we can mean two things: They love their own lives (separate lives) . They love the life that they are having together or share. Example: 'Software developers love their life' would mean that software developers love the life of software ...