在平面圖形上，一個非凸面的立方體或一組點，例如圓圈或球面朝內凹陷的內部曲線。若被割線截斷的弧形線段，均位於某點或某條線的割線對邊，則該曲線的弧形則朝該點或該條線凹陷。凹多邊形的內角一定大於180度。

凹面(P,,U,繁體中文-偏好,D,,)
凹形(,U,繁體中文-非偏好,UF,U,U)
ao mien (P,,U,韋氏拼音-偏好,UF,U,U)
āo miàn (P,,U,漢語拼音-偏好,UF,U,U)
ao mian (P,,U,漢語拼音(無聲調)-偏好,UF,U,U)
concave(P,,U,英文-偏好,D,U,U)
concaaf(P,,U,荷蘭語-偏好,D,U,U)
cóncavo(P,,U,西班牙語-偏好,D,U,U)

藝術與建築詞典根目錄
....物理特質層面
........特質與屬性 (層級名)
............<特質與屬性 (先導詞)>
................<依特定類型區分之特質與屬性>
....................<形式特質>
........................形狀
............................曲線狀的
................................凹面

distinguished from....

凸面

英文....	Of a plane figure, a solid or a set of points that is not convex, for example, hollowed out like the inner curve of a circle or sphere. An arc of a curve is concave toward a point or line if every segment of the arc cut off by a secant lies on the opposite side of the secant from the point or line. A concave polygon always has an interior angle greater than 180 degrees.
荷蘭語....	Uitgehold zoals de binnenste ronding van een cirkel of een bol.
西班牙語....	Ahuecado hacia afuera como la curva interior de un círculo o esfera.

凹面............	[AS-Academia Sinica]
.................	國家教育研究院－雙語詞彙、學術名詞暨辭書資訊網 July 5, 2010
.................	智慧藏百科全書網 January 30, 2012
concave............	[VP]
.................	Putnam and Carlson, Architectural and Building Trades Dictionary (1974) 113
.................	Webster's Third New International Dictionary (1961) 469
.................	Oxford English Dictionary Online (2002-)
.................	Encyclopedia Britannica Online (2002-)
concaaf............	[Bureau AAT]
.................	AAT-Ned (1994-)
cóncavo............	[CDBP-DIBAM]
.................	Moliner, Diccionario de uso del español (2004) I:1326
Subject:............	[Bureau AAT]
.................	Van Dale hedendaags Nederlands (1994)

Getty AAT: 300010302 Getty AAT: http://www.getty.edu/vow/AATFullDisplay?find=costume&logic=AND¬e=&subjectid=300010302
聯合目錄： 凹面 、凹形 、ao mien 、āo miàn 、ao mian 、concave 、concaaf 、cóncavo