## cis conformation

in polymers
Also contains definition of: trans conformation in polymers
https://doi.org/10.1351/goldbook.C01088
@C01258@ referring to torsion angles θ (A, B, C, D), where A, B, C, D are main-chain atoms, can be described as: cis or @T06406-1@ ($$\text{C}$$); @G02593@ or @T06406-2@ ($$\text{G}$$); @T06406-4@ ($$\text{A}$$); and @C01092@ or @T06406-3@ ($$\text{T}$$), corresponding to torsion angles within ± 30° of, respectively, 0°, ± 120° and ± 180°. The letters shown in parentheses (upper case $$\text{C}$$, $$\text{G}$$, $$\text{A}$$, $$\text{T}$$) are the recommended abbreviations. The symbols $$\text{G}^{+}$$, $$\text{G}^{-}$$ (or $$\text{A}^{+}$$, $$\text{G}^{-}$$, for example) refer to torsion angles of similar type but opposite known sign, i.e. ~ +60°, ~ -60° (or ~ +120°, -120°). The notation $$\text{G}$$, $$\bar{\text{G}}$$ ; $$\text{A}$$, $$\bar{\text{A}}$$ (and $$\text{T}$$, $$\bar{\text{T}}$$ ; $$\text{C}$$, $$\bar{\text{C}}$$ - whenever the torsion angles are not exactly equal to 180° and 0°, respectively) is reserved for the designation of @E02079@ conformations, i.e. conformations of opposite but unspecified sign. Where necessary, a @D01650@ from the proper value of the @T06406-5@ can be indicated by the sign (~), as in the following examples: $$\text{G(~)}$$; $$\text{G}^{+}\text{(~)}$$; $$\text{G}^{-}\text{(~)}$$.
Source:
Purple Book, 1st ed., p. 41 [Terms] [Book]