How do you know whether it is a long vowel or short one?

[ardmore]

When I read a sentence, how can you know if a vowel is the a long vowel or short one in a word?
Suppose we don't look up a dictionary?

[BobK]

There are rules - that are almost reliable in distinguishing say 'mitt' from 'mite' (and 'might'). But the only way to distinguish say 'treason' (with /i:/) from 'treachery' (with /e/) is to use a dictionary (or be exposed to a lifetime's native-user input). And distinguishing between the 'long' vowels in 'daughter' and 'laughter' is something that can't be predicted anyway.

Is there any reason for choosing not to use a dictionary?

b

[ardmore]

Well, sometimes I don't know how to read the name such as "vicar". The name can not be found in the dictionary.
I believe that there is a rule.

[5jj]

The word 'vicar' appears in most dictionaries.

Most dictionaries do not list names, though many can be found in the Longman Pronunciation Dictionary and the Cambridge English Pronouncing Dictionary.

[BobK]

Well, sometimes I don't know how to read the name such as "vicar". The name can not be found in the dictionary.
I believe that there is a rule.

Good for you! vicar - /vɪkǝ/ ; mica - /maɪkǝ/ ; chic - /ʃi:k/. There are patterns, but rules...?

b