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A term sometimes used to denote a period parallelogram of a [[Double-periodic function|double-periodic function]]  $  f $
whose sides do not contain poles, and which is obtained from a fundamental period parallelogram by translation over a vector  $  z _ {0} \in \mathbf C $.

====References====
<table><TR><TD valign="top">[1]</TD> <TD valign="top">  E.T. Whittaker,   G.N. Watson,   "A course of modern analysis" , Cambridge Univ. Press  (1927)</TD></TR></table>

====Comments====
In addition there are several technical meanings of the word cell in geometry and topology. Thus, in affine geometry the convex hull of a finite set of points is sometimes called a convex cell. A subset  $  E $
of a topological Hausdorff space such that there is a relative homeomorphism  $  \alpha :  ( B  ^ {n} , S ^ {n - 1 } ) \rightarrow ( \overline{E}\; , \partial  E) $
is a (topological)  $  n $-
dimensional cell. Here  $  B  ^ {n} $
is the unit ball, its boundary  $  \partial  B  ^ {n} = S ^ {n - 1 } $
is the  $  ( n - 1) $-
dimensional sphere, and a relative homeomorphism is, of course, a continuous mapping  $  \alpha :  B  ^ {n} \rightarrow \overline{E}\; $
such that  $  \alpha ( S ^ {n - 1 } ) \subset  \partial  E $
and  $  \alpha $
induces a homeomorphism  $  B  ^ {n} \setminus  S ^ {n - 1 } \rightarrow \overline{E}\; \setminus  \partial  E $; 
cf. also [[Cell complex|Cell complex]] and [[Cellular space|Cellular space]]. The phrase unit cell occasionally occurs as a synonym for the ball (disc) of radius one centred at the origin in  $  n $-
dimensional Euclidean space, and any space homeomorphic to it is also sometimes called an  $  n $-
dimensional topological cell. Finally, cell is sometimes used to denote the possible locations of entries in a matrix or similar structure, such as a [[Magic square|magic square]] or [[Young diagram|Young diagram]], or as a synonym for a block in a block matrix.