Note that we deem eukaryotic cilia and microtubule-based flagella to be equivalent, while the bacterial- and archaeal-type flagella have a different structure. The former are microtubule-based structures that lash back and forth and are present only in eukaryotes, while the latter achieve motility by rotation. Bacterial- and archaeal-type flagella are superficially similar but have a different molecular composition and fine structure. These three structures never co-exist in the same organism. Therefore, GO:0001539 'cilium or flagellum-dependent cell motility' is in the subset of terms that should not be used for direct gene product annotation. Instead, select a child term. Direct annotations to GO:0001539 'cilium or flagellum-dependent cell motility' may be amended during annotation QC.