partially or partly? These two words are often interchangeable, but there is a subtle distinction between them that is worth noting. Partly is the preferable choice with the meaning ‘as regards one part’: The building is constructed partly of brick and partly of stone. Partially is the preferable choice with the meaning ‘to a limited extent; incompletely’: partially sighted. Partly is used more commonly than partially to introduce an explanatory clause or phrase, sometimes in the expression partly … partly: Partly because of the weather and partly because of the weak economy, profits were down last year