Correct spelling, explanation: the word leaves is an Old English word, which came from Old Germanic languages. The word hasn’t changed much over the centuries and has remained in its original form. The singular form of this noun is leaf and it is worth noticing that the plural – leaves – is irregular.

Definition of leaves:
1. noun (plural) – a flat, green part of a plant or tree,
This tree has such unusual leaves that I need to take a photo of it.
2. noun – refers to thin layers of paper,
Some leaves of this book are loose so I will repair them later.

Collocations with leaves:
Some common collocations include autumn leaves, dry leaves, and tea leaves:
I love this time of the year when there are beautiful autumn leaves everywhere.
Dry leaves may become a beautiful decoration when well exposed.
Please put the tea leaves into the bin after you’ve drunk your tea.

Incorrect spelling, explanation: the most basic English rule of forming plural nouns in English is by adding the (e)s ending to a singular noun. This rule, however, doesn’t always apply as when a noun ends in -f or -fe, we change it to -v and then add -es ending. Some users of English tend to forget about it and they create the plural form of leaf as leafs, but it is wrong and the only correct version is leaves.