Sylfan, n. foundation
Sylfaen, n. foundation stone
Sylfaenu, v. to found
Sylfaenydd, n. founder
Sylw, n. a view; remark; notice
Sylwad, n. observation; a regarding; a noticing
Sylwedd, n. substance, matter
Sylweddiad, n. a substantiation
Sylweddol, a. substantial
Sylweddoli, v. to make substantial