de / de / de 的/地/得 (attributive, adverbial, complement)

When a word describes HOW an action is done, it needs adverbial 地 before the verb, not attributive 的. ✗ 她高兴的说谢谢你。 ✓ 她高兴地说谢谢你。(Tā gāoxìng de shuō xièxie nǐ.) — She happily said thank you. Here 高兴 describes the MANNER of 说 (saying), so 地 is required. They sound identical, so examiners check the right character is written.

Putting 的 straight after a verb when the following words give the DEGREE or RESULT is wrong -- that job belongs to 得. ✗ 他跑的很快。 ✓ 他跑得很快。(Tā pǎo de hěn kuài.) — He runs very fast. ✗ 她跳舞跳的很好看。 ✓ 她跳舞跳得很好看。(Tā tiàowǔ tiào de hěn hǎokàn.) — She dances very beautifully. 的 would wrongly treat 很快 / 很好看 as if they described a noun, which they do not.

When the verb has its own object (打篮球, 说汉语, 写汉字), 得 must still attach to a VERB, so the verb has to be repeated. ✗ 他打篮球得很好。(得 wrongly attaches to the noun 篮球.) ✓ 他打篮球打得很好。(Tā dǎ lánqiú dǎ de hěn hǎo.) — He plays basketball very well. Dropping the repeated verb leaves the sentence grammatically incomplete, with no verb for 得 to attach to.

In the writing paper (Paper 1) you must write the CHARACTER, not pinyin: the wrong 的/地/得 is a character-accuracy error, and a pinyin "de" is not credited at all. ✗ 他跑de很快 (pinyin de). ✓ 他跑得很快。(Tā pǎo de hěn kuài.) — He runs very fast. A pinyin "de" is only ever tolerated in the Listening paper, never in writing.

When a descriptive phrase comes before a noun, do not drop the linking 的. ✗ 这是一本有意思书。 ✓ 这是一本有意思的书。(Zhè shì yì běn yǒuyìsi de shū.) — This is an interesting book. 有意思 describes the noun 书, so 的 must join them. Two-syllable and longer descriptions especially need 的; leaving it out makes the phrase ungrammatical.

地 and 得 sit on opposite sides of the verb: 地 comes BEFORE the verb (manner), 得 comes AFTER it (degree/result). Do not swap their positions. ✗ 他说地很清楚。 ✗ 他高兴得说。 ✓ 他说得很清楚。(Tā shuō de hěn qīngchu.) — He speaks very clearly. ✓ 他高兴地说。(Tā gāoxìng de shuō.) — He speaks happily. Check what sits either side of the verb before choosing.

Because all three sound like "de", learners assume any one will do since a reader still gets it. WRONG: they are three separate characters, each with a fixed position (的 noun, 地 verb, 得 after a verb), and the exam marks the wrong one wrong even when the meaning is clear. ✗ 他跑的很快 for 他跑得很快: only 得 fits after 跑, because 很快 is the degree of running, not a noun.