Full Idea
The form of depiction is the possibility that the things are combined with one another as are the elements of the picture.
Gist of Idea
The 'form' of the picture is its possible combinations
Source
Ludwig Wittgenstein (Tractatus Logico-Philosophicus [1921], 2.151)
Book Reference
Wittgenstein,Ludwig: 'Tractatus Logico-Philosophicus (Pears)', ed/tr. Pears,D. /McGuinness,B. [RKP 1961], p.9
A Reaction
This is why 'model' (or even 'simulation'?) is a better term than 'picture' for his proposal. Pictures are fixed, but models can be adjusted.