a hollow / cave

introduction (e.g. of a new idea)

introduce

pupil, student (a child who goes to elementary school) / (law) child, juvenile, person(s) under 18 years of age under the Japanese Child Welfare Law

riot

schoolmate, graduates of the same school / alumnus, alumni

a person beyond the age of retirement who continues to work

two or more words derive from the same source; cognate

a road, a roadway, a carriageway / (more specifically, legal) a traffic lane: that portion of a road that is marked for use by automobiles (and not for bicycles or pedestrians)

kyudo