From Wiktionary, the free dictionary
selo in sitelen pona
From Esperanto ŝelo (“skin”).
selo
- the outside, surface, outer layer or boundary (e.g. skin, bark, peel, shell)
- (by extension) shape, form
2014 May 25, Sonja Lang, “Preface”, in Toki Pona: The Language of Good, page 7:mi wile pana e selo pini pi toki pona.- I hope to present the language [Toki Pona] in its completed form.