Interior elision takes place in forming compound words. Here the apostrophe is not used. Thus, οὐδείς
a. ὁδί_, τουτί_
b. Interior elision does not always occur in the formation of compounds. Thus, σκηπτοῦχος
c. On the accent in elision, see cross174.
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].