What is the difference between the tanka and haiku?

• Tanka is an older form of poetry
• Tanka contains 31 syllables; Haiku has 17
• Tanka is often written in one line in Japanese; Haiku is traditionally written in three
• Tanka has the syllable count 5-7-5-7-7; Haiku has the count 5-7-5

Here are two examples:

Haiku:

A red crab

hiding in the sand -

pure water

(Fukuda Kodojin)

Tanka:

All day

rain has come down

drop by drop

the pain of your absence

has penetrated me.

(Keith McMahen)