why is ammonia termed as a base through it does not contain `OH^(-)` ions?

The following are equations for dissociations of a compound. NH_(3(aq)) + H_2O_(I) harr NH_(4(aq))^+ + OH_(aq)^(-) Why ammonia is termed as a base though it does not contain OH^- ion?

Why is ammonia termed as Lewis base?

Do acidic solutions contain OH^(-) ions ?

Why does ammonia act as a Lewis base ?

Why does ammonia act as a lewis base?