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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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Additionally – For this word:  the first “A” turns into a u-schwa;  the “dd” combination is pronounced simply as the single letter “d” (this is one of TWO standard pronunciations of this letter combination in The Common Tongue);  then the first “i” is short;  and for the “-tion” suffix – the “ti” combination is pronounced like the un-voiced “sh” combination, and the “o” turns into an i-schwa (this is the standard pronunciation of this suffix in The Common Tongue);  and then for the “-ally suffix – the “a” disappears;  the “ll” combination is pronounced simply like the single letter “l” (this is the standard pronunciation of this letter combination in The Common Tongue);  and the final “y” is pronounced like the long letter “e” (this is the standard pronunciation of this suffix in The Common Tongue).

– /uh-DIH-shihn-ə-lee/ – /ə(ʌ).ˈdɪ.ʃə(ɪ)n.ə.liː/ – Notice also that the stress is on the second syllable –

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See Also:  Add, Added, Adding, & Addition

Learn More About The Word “Additionally” On Wiktionary

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