Several parts combine into one character.

Compound ideograph: two right-hands (又, the original "right hand" pictograph) reaching in the same direction = friend. The encoded ethic: companionship is two people working in the same direction. Where 信 (trust, previous) is "person + word", 友 is "hand + hand" — friendship is action, not just speech. Identical across 繁體 / 新字体 / 简体.

Mandarin: yǒu, dipping 3rd tone. The standard word for "friend" in modern Mandarin is the compound 朋友 (péngyou — note neutral tone on the second syllable). Other key compounds: 好友 (hǎoyǒu, close friend), 老友 (lǎoyǒu, old friend), 友谊 (yǒuyì, friendship — formal), 友情 (yǒuqíng, friendship — emotional). Romantic relationships also use 友: 男朋友 (nánpéngyou, boyfriend), 女朋友 (nǚpéngyou, girlfriend) — the "friend" word does double duty.

Japanese: on-reading ユウ (yū) in compound nouns — 友情 (yūjō, friendship), 親友 (shin'yū, close friend / best friend), 友人 (yūjin, friend — slightly formal), 戦友 (sen'yū, comrade-in-arms). Kun-reading とも (tomo) is the everyday word — 友達 (tomodachi, friend) is hands-down one of the highest-frequency words in Japanese. Note 友達 mixes 友 (kun-reading とも) with 達 (tachi, plural marker), so the word literally means "friend-people" — but is used for both singular and plural friends. Other compounds: 友 (tomo, friend — poetic), お友達 (otomodachi, polite/childlike).

The Japanese tradition of 親友 (shinyū) — "deep friend" — is culturally weightier than the English "best friend"; saying someone is your 親友 is a strong declaration.

Memory aid: two hands reaching the same way — comrades.