爸爸 (bàba) means 'dad' or 'father' — it's the everyday, affectionate term children use, comparable to 'dad' rather than the more formal 父亲 (fùqīn), which is closer to 'father' and used in writing or formal contexts.

The character 爸 is built from 父 (fù, 'father') on top, showing the meaning, plus 巴 (bā) underneath giving the sound. This father-son structure — a meaning component over a sound component — is common in Chinese characters and is called a phono-semantic compound.

爸爸 is normally said with the second syllable in neutral tone in casual speech, though written and taught formally as bàba with the second syllable also technically fourth tone. In fast, natural speech you'll hear it lean toward a light, unstressed second syllable, similar to how 妈妈 (māma, 'mom') and 哥哥 (gēge, 'older brother') work — many kinship terms double the character and soften the second one.

Example: 我爸爸是老师。(Wǒ bàba shì lǎoshī.) — 'My dad is a teacher.'

You'll also hear 老爸 (lǎobà), a more casual, joking way to say 'dad,' similar to saying 'old man' affectionately in English.