Strath- BrE AmE stræθ strəθ —For many speakers, stræθ functions as the strong form of this prefix, used in unfamiliar names or careful style, and strəθ as the weak form, appropriate for familiar names and casual style. This applies in the entries that follow.
STRATH-
Meaning of STRATH- in English
Longman Pronunciation English Dictionary. Английский словарь произношений Longman. 2012