ईथर का सामान्य सूत्र R-O-R या (R-O-R') होता है। ईथर में दो एल्किल समूह एक ऑक्सिजन परमाणु द्वारा संयोजित रहते हैं। एल्किल समूह के आधार पर ईथर दो प्रकार के होते है

In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom bonded to two organyl groups. They have the general formula R−O−R′, where R and R′ represent the organyl groups. Ethers can again be classified into two varieties: if the organyl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers. A typical example of the first group is the solvent and anaesthetic diethyl ether, commonly referred to simply as "ether". Ethers are common in organic chemistry and even more prevalent in biochemistry, as they are common linkages in carbohydrates and lignin.