#by the way

• By the way — An adverb used to spontaneously introduce a remark, memory, or digression directly or indirectly related to the topic under discussion; as a neuter noun, it designates a subtle allusion, an incidental remark, a fine irony, or an indirect suggestion made within a conversation.
• By the way — An etymological graphic variant for the noun and adverb 'apropo'; a subtle allusion, passing remark, or indirect suggestion made within a dialogue. As an adverb, it is used to spontaneously introduce a digression or memory structurally linked to the current topic.
• Apropos — A very rare, learned, or archaic form borrowed from Italian, used in pre-modern texts as a structural equivalent for 'by the way' or 'opportunely'; it serves to introduce an incidental remark or indicates that an action happens exactly at the right moment.