| Janus | janitor |
| jejunus | dine, diner, dinner, jejune |
| jocus | jeopardise, jeopardy, jewel, jeweller, jewellery, jocose, jocular, jocularity, joke, joker, juggle, juggler |
| juncus | jonquil, junket |
| jungo | adjoin, adjunct, conjoin, conjoint, conjugal, conjugate, conjugation, conjunction, conjunctive, disjoin, disjoint, disjointed |
| juniperus | gin (a liquor), juniper |
| Juppiter (Jovis) | jovial, jovially |
| jus (right) | abjure, adjuration, adjure, adjust, adjustable, adjuster, adjustment, conjuration, conjure, conjurer, conjuror, injure, injurious, injury, injustice, jurisdiction, jurisprudence, jurist, juror, jury, juryman, just, justice, justifiable, justification, justify, justly, maladjustment, perjure, perjury, readjust, readjustment, uninjured, unjust, unjustly |
| jus (broth) | juice, juicy |
| juvenis | juvenile, rejuvenate, rejuvenator |
| juvo | adjutant, aid, aide, aide-de-camp, coadjutor, jocund, unaided |
| juxta | s. jungo |
