Pronunciation rules for the vowel combination oa

Combination of vowels Pronunciation Example words Example word pronunciation My own example words
oa /ō/ boat /bōt/
/ö/ a broad /ə-bröd/
black·board /’blǎk-börd/

The first pronunciation of the vowel combination oa is the long vowel /ō/ of the vowel o, as in the words bōat and cōat; its second pronunciation is the double-dotted vowel /ö/ of the vowel o, As in the word a bröad, especially when oa occurs in the r-syllable letter combination oar, as in the words black böard and röar. At this time, the r-syllable letter combination oar is pronounced as /ör/, that is, black board and roar (ör).

The following sentence includes two pronunciations of the vowel combination oa, namely /ō/ and /ö/, please memorize this sentence:
Please draw a small boat on the blackboard. Please draw a small boat on the blackboard.