Extending Sounds, First Vocabulary Post

* あお (ao) blue
* あか (aka) red
* あき (aki) autumn

* いぬ (inu) dog
* いもうと (imōto) little sister
* いいえ (īe) no

* うえ (ue) above
* うさぎ (usagi) rabbit
* うなぎ　(unagi) eel

* えいご (eigo) English
* えき (eki) station
* えんぴつ (enpitsu) pencil

* おおきい (ōkī) big
* おちゃ (ocha) tea
* おんな (onna) woman

One can extend the vowel sound of a kana by affixing either a あ、い、or う depending on the vowel. The vowel would be extended for one more mora or beat. In most cases, あ follows あ; い follows い or え and う follows う or お.

There are rare exceptions where an え vowel is extended by adding え or an お vowel is extended by お. Some examples of this include おねえさん (onēsan) "older sister", おおい, and おおきい (ōkii) "larger".

One giveaway to an English-speaking accent in Japanese speech is the use of a diphthong for the elongated "e" sound (Such as the sound in "Eight"). In actuality, "えい" is pronounced correctly by saying the え kana for a longer duration of time.

It is important to make sure you hold the vowel sound long enough because you can be saying "middle-aged lady" （おばさん）(obasan) instead of "grandmother" （おばあさん）(obāsan) if you do not stretch it out correctly.

source: http://en.wikibooks.org/wiki/Japanese/Kana/Lessons/Hiragana/Lesson_1