Theater, an early Middle English borrowing from French, originally had its primary stress on the second syllable:

[French tey-ah-truh]. /French teɪˈɑ trə/. As with many early French borrowings ( beauty, carriage, marriage ), the stress moved to the first syllable, in conformity with a common English pattern of stress, and this pattern remains the standard one for theater today:

[thee-uh-ter]. /ˈθi ə tər/. A pronunciation with stress on the second syllable and the vowel

[ey], /eɪ/, as

[thee-ey-ter] /θiˈeɪ tər/ or sometimes

[thee-ey-ter] /ˈθiˌeɪ tər/ is characteristic chiefly of a nonstandard regional pronunciation in the United States that may be perceived as uneducated.

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