In Japanese, one is continually fitting new parts onto words and transforming them into new words by using helper verbs

For example:

• Japanese Passive
• How そう actually works

In Japanese, one does not conjugate. Instead, one crafts new words by changing their endings.

For example:

• 美味しい -> 美味しくない -> 美味しくなさそう
• = tasty -> not tasty -> “not tasty looking”

Stems §

• あ
  • ーない
  • ーれる (Japanese Passive)
  • ーせる ((Japanese Causative Form))
• い
  • ーます
  • ーたい
  • ーそう
  • ーすぎる
• う (→ default)
• え
  • ーる (potential form)
  • ーば (conditional)
• お
  • ーう (volition form)

Note §

From Unlocking Japanese

What is actually happening is that, while English adds words to express many concepts, Japanese turns one word into another word that carries the new meaning. Sometimes that process is really a conjugation in the European sense, but very often it isn’t.