word choice - What's the difference between 女性 and 女の人?

As far as I'm aware, both words translate into English as "woman". What's the difference in meaning between 女性 and 女の人?

Answer

There is no difference in meaning when the two words refer to "woman/women". There are, however, differences in how native speakers perceive the two words and the nuance they carry.

To discuss the exception first, 「[女性]{じょせい}」, has an extra meaning "feminine" or "female gender" when used in grammar terms for certain languages such as Romance languages. For instance, "la maison = 'the house'" is a 「[女性名詞]{じょせいめいし}」 = "feminine noun" in French. We never call it an 「女の人名詞」 or 「女名詞」.

As with nearly all other pairs of Japanese-origin words and their Chinese-origin counterparts with the same or similar meanings, the main difference between the two groups is the formality of the words. On-reading, Sino-loanwords like 「女性」 are almost always used in more formal or technical situations than their kun-reading, Japanese-origin counterparts like 「女の人」.

Japanese children learn to use the word 「女の人」 years before they learn to actively use 「女性」. You would rarely meet a kid under 12 or so who uses 「女性」 on a regular basis. Even teenagers would rarely use 「女性」 in their daily conversations, but they would in compositions and presentations in schools.

Some adults use 「女性」 even in the most informal conversations, but using 「女の人」 would be far more common on those occasions. Only 「女性」 is used in newspapers, magazines, academic papers, etc., and using 「女の人」 in those is utterly out of the question.