Lossy compressors don't have the same constraints as a lossless compressor. If you data your input, compress it, and then decompress it, the output is not identical to the input. This allows the compressor to potentially compress the data far more than even the ideal lossless compressor hypothesized above.
The question mark (?), also known as the interrogation point, query, and eroteme, is a punctuation mark that indicates an interrogative clause, or phrase in many languages. The question mark is not used for indirect questions.
A sign is a clue something happened, or a display that communicates a message, like a stop sign that tells you stop. To sign also means to write your signature. The word sign has many senses, but in a general, it usually has something to say. It may be a symptom that tells about a problem, or it may just be a symbol, like the plus and minus signs in math. Sign language uses hand signals to represent words and letters.