This is the 4212th most frequent Japanese word.
五月
"五月" means "May" (the fifth month of the year).
The word '五月' represents the month, in this case, May, used as the subject to describe the season.
五月は春の終わりです。
May marks the end of spring.
Here, '五月' indicates the specific time of the year when the birthday occurs.
あなたの誕生日は五月ですね。
Your birthday is in May, isn't it?
'五月' is used to describe the characteristic freshness associated with nature during this month.