転音

In Japanese, ten'on 転音, also called boin koutai 母音交替, "vowel change," is a change in pronunciation where the vowel of a morpheme changes in order to connect to another morpheme in a word.

Examples include:

• fune-ashi ふねあし
  funaashi ふなあし (舟足)
  Boat speed.
• kaze-kami かぜかみ
  kazakami かざかみ (風上)
  Upwind.
• kami-nagara かみながら
  kamunagara かむながら
  As a god.
  As in the age of gods.
• ame-kasa あめかさ
  amagasa あまがさ (雨傘)
  Umbrella.
• sake-taru さけたる
  sakadaru さかだる (酒樽)
  Alcohol barrel, cask.
• ue-ki うえき
  uwagi うわぎ (上着)
  Outer garment. Coat.
• ki-tachi きたち
  kodachi こだち (木立)
  Tree grove.

Note: in the words above, ka becoming ga, ta becoming da, and ki becoming gi consist of a different change in pronunciation called rendaku 連濁.

References

• 転音 - kotobank.jp, accessed 2019-11-11.