Waka is a style of verse usually containing thirty-one syllable in five lines.
It follows a 5-7-5-7-7 syllable pattern.
Waka is probably the oldest poetic style in Japan.
In Heian period ( 784-1185) the exchange of romantic waka between men and women
of noble families became popular.
However, waka was used almost exclusively by the cobles, and was never very popular
In the past there were several styles of waka.
They were all based on a similar syllable pattern, but had different length.
Over time, however, the five-line style known as tanka became dominant
and is the only style still popular today.
Indeed, the term of tanka has now become synonymous with waka.