It is true, however, that some haiku poems have no season word and, in such cases, those haiku poems were referred to as 'zo no ku' (miscellaneous poems) in hokku (the first line of waka or haiku) of haikai in the Edo period which became known as mukihaiki (haiku without season word) in the modern haiku after the generation of Shiki MASAOKA.
もっとも季語を含まない俳句もあり、その場合には、江戸俳諧の発句では雑（ぞう）の句、子規以降の近代俳句では無季俳句と呼ばれる。