In written Japanese, the length of vowels 長音/cho:on/ is indicated by the syllables あ - a , い - i, う - u, え - e, お - o, which immediately follow them.

あ - a
"a" is lengthened with additional "a": おかあさん (okaasan, “mother”) and おばあさん (obaasan, “grandmother”).

い - i
1)"i" is lengthened with additional "i": おにいさん(oniisan, “older brother”);
2)syllables in words of Chinese origin ending in "e": とけい(tokei , “clock”), がくせい(gakusei, “student”). It is necessary to pronounce here the long sound "e", and not the combination of vowels "ei".

え - e
"e" is lengthened with additional "e": おねえさん (oneesan, “older sister”).

う - u
1)"u" is lengthened with additional "u": ふつう(futsuu, “usually”), くうき(kuuki, “air”), ぐうぜん(guuzen, “accidentally”);
2)in the vast majority of cases is lengthened with additional "o": ひこうき(hikouki, “plane”), れいぞうこ(reizouko, “refrigerator”), ぶんぽう(bunpou, “grammar”). It is necessary to pronounce here the long sound "o", and not the combination of vowels "ou".

お - o
There are exceptions when "o" is lengthened by the syllable "o": おおきい(ookii, “big”), とおり(toori, “street”), とおい(tooi, “far”), こおり(koori, “ice”), とおか(tooka, “tenth number”) etc.

Another important point in the process of mastering Japanese phonetics is the phenomenon of vowel reduction (母音無声化 /boin-no museika/). Depending on the consonant sound before or after the vowel, it happens that the vowel sound in the middle of the syllable is not pronounced. It is useful to remember several phonetic rules:

1) reduction of the vowels "i" and "y" occurs if they are between the voiceless consonants "k", "s", "sh", "t", "ts" , "ch", "f" and "p": 草 (ksa, “grass”), 菊 (kku, “chrysanthemum”);

2) sometimes the vowels "i" and "y" after voiceless consonants at the end of the word undergo reduction if the corresponding syllable is unstressed: あります(arimas, “to be available”, “to be located”), ございます(gozaimas, “to be available”, “to be located /official-polite variant/ “), もつ(mots, “to have with you”, “ to possess”), はし(hash, “chopsticks”);

3) in addition to the already mentioned vowels "i" and "y", which are often reduced, other vowels ("a", "e", "o"), as an exception, can also be reduced: かかし(kkashi, “scarecrow”), ところてん(tkoroten, “agar-agar jelly”), かかと(kkato, “heel”).

Did you know about these rules? Share in the comments your examples!