(I'm) (a)fraid so
A response used to politely answer a question in the affirmative when the speaker regrets that this is the case. When the phrase is abbreviated to "fraid so," an apostrophe is often used in place of the missing letter. A: "Are you really moving all the way across the country?" B: "I'm afraid so." A: "Are you going to be working late again tonight?" B: "’Fraid so."
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
(I'm) afraid so.and 'Fraid so.
I believe, regrettably, that the answer is yes. (The apostrophe is not always shown.) Alice: Do you have to go? John: Afraid so. Rachel: Can I expect some difficulty with Mr. Franklin? Bob: I'm afraid so.
See also: afraid
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.