preface, beginning, order, precedence, occasion, chance, incidentally
序 centers on the idea of a structured beginning or arrangement: a preface that sets the order of things, a sequence, or an occasion that arises as part of that order. The sense of 'chance' or 'incidentally' extends from something that happens in due course.
序 combines 广 (building) with 予, which likely contributes the sound and the idea of arranging or ordering. The character originally referred to the east-west walls of a building, which gave structure to the space, later extending to order and preface.
Inside a building (广), a person is arranging (予) the order of things, like setting up a preface before a main event.
For ジョ, imagine writing a preface for a book about Joe: Joe -> ジョ, and the preface sets the order for the whole story.
opportunity; occasion; chance
opening (in a game of go, chess, etc.)
order; discipline; regularity; system; method
order; sequence
order; ordering
rank; ranking order; hierarchy
preface; foreword; introduction; introductory chapter
disorder; chaos; confusion
overture; prelude
public order and morals; social standards; public policy
preface; foreword; introduction
seniority by length of service
the beginning (as in "this is only the beginning")
inflorescence
introduction
introduction; preface
introduction
traversal sequence
packet sequencing
message sequence integrity