Also found in: Thesaurus, Medical, Legal, Encyclopedia.


1. An opening, such as a hole, gap, or slit.
a. A usually adjustable opening in an optical instrument, such as a camera or telescope, that limits the amount of light passing through a lens or onto a mirror.
b. The diameter of such an opening, often expressed as an f-number.
c. The diameter of the objective of a telescope.

[Middle English, from Latin apertūra, from apertus, past participle of aperīre, to open; see wer- in Indo-European roots.]

ap′er·tur′al adj.


(ˈæpəˌtjʊərəl; əˈpɜːtjərəl)
relating to aperture or an aperture
References in periodicals archive ?
The potential mechanism is more complicated for axial sculpture, where ribs, varices, or lamellae are oriented perpendicularly to the direction of shell growth (parallel to the apertural margin).
Most striking variation was found in the shape class and apertural types.
The massive septa are pierced by large rounded openings, which are disposed in a cribate system occupying almost the entire apertural face.
For bivalve prey, prey shell length was defined as the distance from the anterior margin to the posterior margin of the shell, whereas in gastropods shell length was defined as the distance from the apex to the outermost tip of the apertural lip.
Quinqueloculinasemminula which was described by Howe differs from Quinqueloculinasemminula except this species has extended apertural neck.
ortizdezarateorum, and can be easily distinguished from any other Avakubia species by its shell sculpture and arrangement of the apertural barriers, but also conchometrically (Fig.
Pollen are usually classified on the basis of their shape, size, symmetry, polarity, apertural types and exine sculpturing (Perveen, 1993).
Such taxa are noted to have apical surface structure, an apertural longitudinal grove or channel, and a parietal wall callous (Pilsbry, 1897-1898).
Puesto que la novela tambien es espacio, espacio textual animado por el movimiento vectorizado de la escritura y de la lectura, espacio delimitado por esas lindes precisas que son el incipit y el excipit, espacio fragmentado por la division de la materia narrativa en capitulos o segmentos, divisiones que a su vez generan nuevas lindes internas, el narrador se vale de la armazon de su obra para explorar tal motivo, valiendose ya sea de su ubicacion apertural y/o final, ya sea de su ubicacion central, ya sea de su repetida mencion, pues de lo que se trata no es tanto de relatar la muerte del tirano como de aniquilarlo definitivamente mediante la palabra ficcional.
SEM: tectum very perforate with striate aspect, apertural membrane scabrate (see also Telleria, 2008).
Margo formando pliegue apertural proximo a 1 [micron]m, psilado, ligeramente ondulado.