1To include someone or something within a group, scope, or total - often used as 「〜を含めて」 when counting or accounting for something.
参加費には昼食を含めて三千円です。
The participation fee, including lunch, is 3,000 yen.
新人を含めて、チームは全部で八人になった。
Including the new hire, the team now has eight people in total.
税金を含めた金額を見積もりに書いてください。
Please write the amount including tax on the estimate.
この計画には周辺住民の意見も含めて検討する必要がある。
This plan needs to be considered including the opinions of local residents as well.
2To explain something to someone carefully and patiently so they fully understand - often used for instructing a child or subordinate. A somewhat formal/old-fashioned usage.
母は子どもに危険な理由を含めて説明した。
The mother carefully explained to her child the reasons it was dangerous.
先生は生徒たちに規則の意味をよく含めて聞かせた。
The teacher patiently explained the meaning of the rules to the students so they'd understand.
3To convey a meaning or feeling indirectly through words, without stating it outright - to imply or hint at something.
彼女は不満を含めた言い方で返事をした。
She replied in a way that implied dissatisfaction.
上司は皮肉を含めて「よくやったね」と言った。
The boss said 'well done' with a hint of sarcasm.
4To put something, such as medicine or candy, into someone's mouth - used as 「口に含める」.
看護師は患者の口に薬を含めた。
The nurse put the medicine in the patient's mouth.
5To infuse a dish or liquid with flavor, letting it permeate throughout.
だしのうま味を十分に含めた煮物を作った。
I made a simmered dish well infused with the flavor of the dashi broth.