Charles Ellicott Commentary John 11:27

"She saith unto him, Yea, Lord: I have believed that thou art the Christ, the Son of God, [even] he that cometh into the world." — John 11:27 (ASV)

She saith unto him, Yea, Lord.—This is her assent to the question He asked. She believed all that He had told her. It is not that she expresses her belief, in answer to His question, in the remainder of this verse. The answer is simply Yea, Lord. Then she proceeds to give the foundation on which that answer rested.

I believe that thou art the Christ.—The word means, “I have believed, and do now;” “I have convinced myself, and do believe.” But this being so, convinced that He is the Messiah, she has in that conviction the ground for believing all that He has now taught her of Resurrection and Life.