To pay (money or a bill). Note: 支 in 支払う is sometimes used as ateji (phonetic).
店で晩ご飯の代金をクレジットカードで支払った。
I paid for dinner at the restaurant with a credit card.
家賃は毎月１０日までに支払ってください。
Please pay the rent by the 10th of each month.
ネットで商品の代金を先に支払う必要がある。
You need to pay for the item online in advance.