It takes one to know one. Aithníonn ciaróg ciaróg eile. Silence is golden. Is binn béal ina thost. Faraway hills are greener. Is glas iad na cnoic i bhfad uainn. A hint is enough for the wise. Is leor nod don eolach. Necessity is the mother of invention. Múineann gá seift.