おばあさん
おばあさん · obaasan · JLPT N5 · noun
grandma
👵 o (polite) + baa (granny) + san (Mrs) — long aa, unlike obasan = aunt
Honorific o + baba (old woman, shortened to baa) + san. The stretched aa is what matters: obasan with a short a means aunt. Older woman, longer vowel. The same trick splits ojiisan (grandfather) from ojisan (uncle).