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A mother's good intention does not always lead to expected results.

Sometimes, we read an article a as [ə;](1), and at other times as [eɪ](2).

I heard one read the 'A' in above sentence as [eɪ].

Is there a time appropriate for #1 and #2?
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It is a matter of stress. [ei] is the emphasized version, while [ə] is the unmarked version.
Comments  
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Hi,

So you mean when we use [ei] the stress will lie upon the number of sth?

Thank you in advance,

Iman
Not necessarily; the article is emphasized for some contextual meaning.
Your concern is highly appreciated.

Regards,

Iman
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