The word 会 (huì) can be used to express an ability that has been learned (a skill). In this case 会 (huì) is an auxiliary verb.
Subj. + 会 + Verb + Obj.
This structure is the easiest way to express all kinds of skills, from languages, to sports, to skills in daily life such as cooking and driving.
- 他 会 说 中文。Tā huì shuō Zhōngwén.He can speak Chinese.
- 我 会 写 汉字。Wǒ huì xiě Hànzì.I can write Chinese characters.
- 你 会 做饭 吗？Nǐ huì zuòfàn ma?Can you cook food？
- 狗 会 唱 歌 吗？Gǒu huì chànggē ma?Can dogs sing？
- 爸爸 会 开车。Bàba huì kāichē.Dad can drive.
Negating 会 (huì) Sentences
会 (huì) sentences are negated with 不 (bù), which is inserted in front of 会 (huì):
Subj. + 不 + 会 + Verb + Obj.
Again, this is the simplest way to express the lack of a learned ability. So while "can't" is a natural translation for "不会" (bù huì) in English, "don't know how to" is equally correct (and perhaps more helpful).
Also, due to a tone change rule for "不" (bù), the phrase "不会" (bù huì) is actually pronounced "bú huì."
- 我 不会 说 英文。Wǒ bù huì shuō Yīngwén.I can't speak English.
- 妈妈 不会 做 中国 菜。Māma bù huì zuò Zhōngguó cài.Mom can't cook Chinese food.
- 你 不会 游泳 吗？Nǐ bù huì yóuyǒng ma?You can't swim?
- 我 奶奶 不会 用 电脑。Wǒ nǎinai bù huì yòng diànnǎo.My grandmother can't use a computer.
- 你 不会 开车 吗？Nǐ bù huì kāichē ma?You can't drive a car?
Note that if we say 我不能说中文 (wǒ bù néng shuō Zhōngwén), the speaker is saying that he can't speak Chinese for some reason other than his own ability, perhaps because speaking Chinese in English class is forbidden.