noun, adverb
Often used in the pattern ～もろとも to mean 'together with' or 'along with', frequently in contexts of shared fate or simultaneous action.
船は乗組員もろとも沈んだ。
The ship sank together with its crew.
彼は家族もろとも田舎に引っ越した。
He moved to the countryside together with his family.
一緒に is the common word for 'together'; もろとも implies a stronger sense of shared fate or being involved together, often in negative or dramatic situations.
Compound of 諸 (moro, 'both, all') and 共 (tomo, 'together'). The exact historical derivation is uncertain, but the word has been used since classical Japanese.