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The pronunciation of any word in English (or any language at all) is not Universal.  This is because there are many different dialects of The English Language — both throughout America, and also world-wide.  The pronunciations that are presented on GiveMeSomeEnglish!!! are based-upon a combination of both “common usage”, and the most neutral accent used in The International Common Tongue — a.k.a. “American English”.
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Activities – For this word:  the “A” is short;  the “c” is hard but is (usually) stopped;  the first “i” is short;  the second “i” turns into an i-schwa;  the second “t” (usually) turns into the flap-t;  the “ie” combination is pronounced simply like the single long letter “e” (this is the standard pronunciation of this letter combination in The Common Tongue);  and the final “s” is pronounced (almost) like the letter “z”.

– /æk-TIH-vih-deez/ – /æk.ˈtɪ.və(ɪ).ɾiːz/ – Notice also that the stress is on the second syllable –

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See Also:  Act, Acted, Action, Actions, Activate, Active, Actively, Activists, Activity, Actor, Actors, Actress, & Actresses

Learn More About The Word “Activities” On Wiktionary

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