when you have two syllables, one consonant and one vowel in a word and second syllable is stressed ,when you add suffix(ed,ing,er,en) you have to double the last word except from few exceptions.
forget-forgetting
forbid-forbidden
and so on ...
so my question is how should I know if the first syllable is stressed or the second one?
Top answer
You'll need to look up the word in a dictionary that shows pronounciations.
— Vorpar
You'll need to look up the word in a dictionary that shows pronounciations.
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If you have been practicing your pronunciation, you should be able to hear which syllable is stressed without even looking it up in the dictionary.
The stressed syllables of these verbs are in bold. You should stress them when you say them. If you say them correctly, you don't really need the dictionary to determine stress.
There is a standard set of rules for American English, and another (very slightly different) for British English, as Yankee mentioned above. You'll have to decide which of the two you want to follow and stick to that version.