柚 (yòu) is the single-character form. The more common spoken form is 柚子 (yòuzi). In some dialects, 柚 can also refer to teak wood — context will clarify meaning.
Tree radical on the left marks 柚 as a kind of tree — the pomelo or grapefruit tree. Same radical groups most fruit-bearing trees: 桃 peach, 李 plum, 梨 pear, 桔 tangerine.
Right side supplies the sound: yóu → yòu (tone shift). 由 also visually resembles a fruit with a stem on top, which works as a memory hook even though it is not the historical source of the image.
