(idiomatic) Something ordinary or run-of-the-mill. / (idiomatic) Nothing worth discussing; nothing that the speaker wants to mention.

(photography) The ratio of the focal length of a lens to its diameter; a measure of the light-gathering ability of the lens.

Alternative form of Erdős number

(mathematics) A number describing the degree of collaboration between a mathematician and Paul Erdős, defined such that a mathematician who has written a paper with Erdős has an Erdős number of 1, a mathematician who has written a paper with somebody having an Erdős number of 1 has an Erdős number of two, and so on.

A number allocated to a syllable in various transliteration systems such as Hanyu Pinyin indicating the tone in which it is pronounced.

(idiomatic) To lack support, as in an argument, debate, or negotiation.

Alternative spelling of non-governmental organization

A telephone number dialled by mistake, for example by transposing digits. / A telephone call received from an unfamiliar caller, due to a mistake in the number dialled.

(idiomatic) An event where patrons are enticed to buy entry tickets into some venue, for example a movie theater, with the anticipation that they will be entered into a drawing to win an amount of money if their ticket is drawn and they are on-site at the time of the winning.

(set theory) A mathematical notation for describing a set by specifying the properties that its members must satisfy.