These clauses form part of the contract between buyer and seller.
《牛津词典》
2
根据共同保险条款,保险人通常必须付全部费用的百分之二十。
According to co-insurance clauses, the insured person must pay usually 20 percent of the total expenses covered.
3
如果提供商提供一份标准格式合同(通常的惯例是这样的),那么你必须对所有的条款和条件都十分地清楚。
If the vendor provides a standard form of contract (which is a general practice), then you must be must be fully aware of all the terms and conditions.