A flagellate is an organism with one or more whip-like organelles called flagella. Some cells in may be flagellate, for instance the spermatozoa of most phyla. do not produce flagellate cells, but , , green algae, some gymnosperms and other closely related plants do. Likewise, most fungi do not produce cells with flagellae, but the primitive fungal do. Many take the form of single-celled flagellates.
A coupling (or a coupler) is a mechanism for connecting rolling stock in a train. The design of the coupler is standard, and is almost as important as the track gauge, since flexibility and convenience are maximised if all rolling stock can be coupled together.
