• 児童じどう — children (esp. in school)
• 小児しょうに — young child, infant
• 育児いくじ — childcare
• 孤児こじ — orphan
• 幼児ようじ — toddler
• 愛児あいじ — beloved child

児 is the simplified form of 兒, which originally showed a child with hair tied in a traditional style. The radical 儿 (ひとあし) represents legs or a child figure. This kanji is commonly used in compound words related to young people.

児童じどうは 学校がっこうで 勉強べんきょうします。
Children study at school.

小児しょうにの 病気びょうきに 詳くわしい 医者いしゃが 必要ひつようです。
A doctor with expertise in childhood illness is needed.

🎧 The on-yomi “ジ” appears in many compound words related to children. The kun-yomi “こ” is rarely used on its own in modern compounds but is historically meaningful.