凹 (āo): concave, depressed, sunken, indented, female (connector etc), (used in names)

凹 (āo) is a Chinese character meaning “concave.” Classified as HSK Level 7-9 (HSK 3.0 Standard, CLEC 2022), it is composed of 一 (structural). It ranks #2670 in character frequency (SUBTLEX-CH corpus).

Etymologically derived, 凹 a rectangle with a hollow. Its radical form 凵 (open mouth) appears in many related characters such as 出 (chū, to go out), 击 (jī, to hit), 凶 (xiōng, terrible).

Spoken pronunciation

HSK 7-9 Radical: 凵 open mouth5 strokesFrequency #2670一 structural

Definitions

concave
depressed
sunken
indented
female (connector etc)
(used in names)

Etymology & Origin

凹

ideographicA rectangle with a hollow

Components:一structural

Stroke Order

Practice writing 凹 with real-time feedback — trace each stroke in the correct order and build muscle memory in the HanziFeed app.

Words & Compounds

Common Compounds

Word	Pinyin	Meaning
凹陷verb	āo xiàn	to cave in
凹槽noun	āo cáo	recess
凹凸adjective	āo tū	concave or convex
凹坑	āo kēng	concave depression
凹凸不平phrase	āo tū bù píng	(idiom) uneven (surface)
凹造型	āo zào xíng	(coll.) to strike a pose
中央凹noun	zhōng yāng āo	fovea centralis (depression in the macula retina, most sensitive optic region)
凹面镜noun	āo miàn jìng	concave mirror
凹进	āo jìn	concave
凹度noun	āo dù	concavity
凹入	āo rù	recessed
凹凸有致adjective	āo tū yǒu zhì	curvaceous
微凹黄檀noun	wēi āo huáng tán	cocobolo (Dalbergia retusa)
胃小凹noun	wèi xiǎo āo	(physiology) gastric pits
山凹noun	shān āo	col

Total compounds

As first character

As last character

As middle character

凹 appears in 31 compound words: 84 as the first character, 13 as the last, and 3 in a middle position. Compound statistics computed from SUBTLEX-CH and HSK 3.0 vocabulary data.

Strongest Collocations

Characters that most frequently co-occur with 凹 in natural Chinese text, ranked by NPMI (Normalized Pointwise Mutual Information) — a statistical measure of association strength.

槽cáo

0.6632,772 co-occurrences

凸tū

0.6471,917 co-occurrences

陷xiàn

0.5874,156 co-occurrences

痕hén

0.464356 co-occurrences

坑kēng

0.434630 co-occurrences

椎zhuī

0.420228 co-occurrences

岖qū

0.41130 co-occurrences

形xíng

0.3951,830 co-occurrences

呈chéng

0.392470 co-occurrences

微wēi

0.387588 co-occurrences

Idioms & Chengyu (2)

凹凸不平āotūbùpíngHSK 7+

uneven; bumpy

phrase

凹凸有致āotūyǒuzhìHSK 7+

having a full figure; shapely; curvaceous; voluptuous

adjective

Example Sentences

AI-Generated

凹字虽然难写，但意思很有趣。

āo zì suī rán nán xiě , dàn yì sī hěn yǒu qù .

The character "凹" may be difficult to write, but its meaning is quite interesting.

中国新闻网_梳理天下新闻Mar 2026

甘肃临泽凹凸棒石点“土”成金的“七十二变”

gān sù lín zé āo tū bàng shí diǎn tǔ chéng jīn de qī shí èr biàn

Gansu’s Linze Attapulgite: Turning Soil into Gold Through 72 Transformations

UdnnewsindexMar 2026

基隆市3车相撞轿车左前门凹陷妇人受困驾驶座消防员破坏车体救人

jī lóng shì 3 chē xiāng zhuàng jiào chē zuǒ qián mén āo xiàn fù rén shòu kùn jià shǐ zuò xiāo fáng yuán pò huài chē tǐ jiù rén

Three-car collision in Keelung City; sedan’s front left door dented; woman trapped in driver’s seat; firefighters cut open the vehicle to rescue her

Cool3cMar 2026

MWC 2026:联想亮相可凹折萤幕掌机与 AI 办公机器人等多款概念...

M W C 2 0 2 6 : lián xiǎng liàng xiāng kě āo zhé 萤 mù zhǎng jī yǔ A I bàn gōng jī qì rén děng duō kuǎn gài niàn . . .

MWC 2026: Lenovo Unveils a Range of Concept Devices, Including a Handheld Console with a Foldable Screen and an AI Office Robot...

東森新聞Feb 2026

...岁少年健身遭190公斤杠铃重击胸口瞬间凹陷

. . . suì shǎo nián jiàn shēn zāo 1 9 0 gōng jīn gàng líng chóng jī xiōng kǒu shùn jiān āo xiàn

... The young man was hit hard by a 190-kilogram barbell and his chest instantly sank

Hk01.comFeb 2026

...回单身后衣着更大胆穿吊带薄纱裙海边大晒凹凸有致身材

. . . huí dān shēn hòu yī zhe gēng dà dǎn chuān diào dài báo shā qún hǎi biān dà shài āo tū yǒu zhì shēn cái

... After returning to singleness, he dressed more boldly, wearing a suspender tulle skirt, and exposed himself to the beach

Character Family

Frequently Asked Questions

What does 凹 (āo) mean in Chinese?

凹 (āo) primarily means "concave." It is classified as HSK Level 7-9, making it an expert-level character. It ranks #2670 in character frequency.

What's the difference between 凹 and 男?

凹 (āo) and 男 (nán) are often confused. antonym. The key distinguishing feature: 凹 (female) vs 男 (male).

How many strokes does 凹 have?

凹 is written with 5 strokes. The correct stroke order matters for recognition and handwriting speed — practice with the animated guide above to build proper technique.

What is the radical of 凹?

The radical associated with 凹 is 凵 (open mouth). This radical appears in many characters related to open mouth.

What are the components of 凹?

凹 is composed of: 一 (structural). Understanding the components helps with both memorization and recognizing related characters.

What are common words containing 凹?

Common words with 凹 include: 凹陷 (āo xiàn, "to cave in"); 凹槽 (āo cáo, "recess"); 凹凸 (āo tū, "concave or convex"); 凹坑 (āo kēng, "concave depression"); 凹凸不平 (āo tū bù píng, "(idiom) uneven (surface)"). There are over 31 compound words containing this character.

What characters sound the same as 凹 (āo)?

Several characters share the pronunciation āo: 奥 ((bound form) Austria (abbr. for 奧地利|奥地利)), 傲 (proud), 澳 (Macao (abbr. for 澳門|澳门)), 熬 (to cook on a slow fire). Context and tones help distinguish between them in speech and writing.

Is 凹 the same in simplified and traditional Chinese?

Yes, 凹 is written the same way in both simplified and traditional Chinese.

Practice writing 凹 with real-time feedback

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