transcytosis

This term describes a specialized mechanism of cellular transport that combines endocytosis and exocytosis to move substances entirely through a cell. It is primarily used in highly technical biological and medical contexts, such as describing how antibodies or hormones cross epithelial layers or the blood-brain barrier.

As a technical scientific term denoting a specific biological process, it is treated as an uncountable noun. It does not have a plural form in standard scientific discourse, as it refers to the general mechanism rather than individual instances of the event.