Learn Hardcore Chinese: tā mǎi le yí jiàn hóngsè de yīfu.

No. 了 after the verb is the perfective aspect marker: it marks the action as completed. In 她买了一件红色的衣服, the buying event is viewed as a whole, completed occurrence. Chinese doesn’t have verb tenses like English; “pastness” is inferred from context and aspect.

Completed event now: 她买了…
Experience (ever before): 她买过…
New situation/already (sentence-final 了): see below on sentence-final 了.

Why is 一 pronounced yí in yí jiàn?

Tone sandhi for 一:

Before a 4th-tone syllable: yí (e.g., 一件 yí jiàn, 一个 yí gè).
Before 1st/2nd/3rd tones: yì (e.g., 一天 yì tiān, 一名 yì míng, 一本 yì běn).
It stays yī when said in isolation, for emphasis, or in ordinals: 第一 dì-yī.

Why do we need 件 here? Could I use 个 instead?

Chinese counts nouns with measure words. 件 is the standard measure word for a single garment or upper-body clothing item, so 一件衣服 = “one piece of clothing.” Using 个 with 衣服 (e.g., 一个衣服) is non-standard.

Common clothing measure words:
- 件: 衬衫 (shirt), 外套 (coat), 毛衣 (sweater), T恤 (T-shirt), and as a general “garment.”
- 条: 裤子 (pants), 裙子/连衣裙 (skirt/dress).
- 双: 鞋(子) (a pair of shoes). One shoe: 一只.
- 顶: 帽子 (hat).
- 套: 西装/套装 (suit/set).

Can I drop 一 and say 她买了件红色的衣服?

Yes. In everyday speech it’s common to drop the numeral but keep the classifier: 她买了件红色的衣服. In careful writing or when you want to stress “one,” keep 一. You cannot drop both the numeral and the classifier.

What’s the role of 的 here? How is it different from 地 and 得?

的 links a modifier to a noun (attributive marker): 红色的衣服 = “red clothing.”

的: adjective/phrase + 的 + noun (红色的衣服).
地: adverbial marker before verbs (高兴地说 “happily said”).
得: follows verbs/adjectives to introduce complements (说得很快 “speak quickly”).

红色的衣服 vs 红衣服 vs 红的衣服—what’s the difference?

All can mean “red clothing,” but with nuance:

红色的衣服: most neutral/standard; clearly treats 红色 (“the color red”) as a classifier-like descriptor.
红衣服: concise and common in speech; monosyllabic color adjectives like 红/黑/白 often drop 的 before certain nouns.
红的衣服: also fine; feels a bit more colloquial or contrastive (“the red (kind) clothes”). Avoid 红色衣服 (without 的) in standard prose; it’s less natural.

Is 衣服 singular or plural in Chinese?

衣服 is a collective/mass noun. It can mean “clothes” in general or “clothing.” To count a specific item, use a measure word: 一件衣服 (“one garment”). Don’t add a plural suffix: 衣服们 is incorrect.

Can I omit 了 and still be correct?

For a specific completed purchase, 了 is normally used. 她买一件红色的衣服 without 了 tends to read as a plan/request or part of a larger construction (e.g., 她要/打算买一件…). In narrative or reporting a completed event, keep 了.

Why does the color phrase go between the classifier and the noun?

The order is: Number + Measure + Modifier + Noun. So you get 一件 + 红色的 + 衣服. The modifier phrase sits right before the noun it describes:

那件红色的衣服 (“that red piece of clothing”)
一件漂亮的衣服 (“a pretty garment”)

How do I say “two red items of clothing”? Do I use 二 or 两?

Use 两 with measure words: 她买了两件红色的衣服. 二件 is generally not used in this context (except in counting/reading numbers).

How do you pronounce 衣服? I’ve heard yīfu and yīfú.

Mainland standard is yīfu with a neutral tone on 服. In Taiwan, yīfú (second tone on 服) is also common. Both will be understood; follow the regional norm you’re learning.

How would I specify the exact garment?

Replace 衣服 with the item and use the right measure word:

她买了一件红色的衬衫 (shirt; 件)
她买了一条红色的连衣裙/裙子 (dress/skirt; 条)
她买了一条红色的裤子 (pants; 条)
她买了一双红色的鞋(子) (shoes; 双)
她买了一顶红色的帽子 (hat; 顶)

Can I say “the red one” without repeating the noun?

Yes. 她买了一件红的 means “She bought a red one.” If referring to a specific known item, use a demonstrative: 她买了那件红色的 (“she bought that red one”).

Can 了 appear at the end too? What’s the difference between 买了 and 买过/买到?

You can have sentence-final 了 as well: 她买了一件红色的衣服了. The first 了 marks completion; the final 了 signals a new situation or “already.”
买了: completed on a particular occasion.
买过: has the experience of having bought (at least once) before.
买到: succeeded in obtaining (focus on achievement), e.g., 她买到了一件红色的衣服 (“she managed to buy one”).