1) Coding 2) Cryptography 3) Decoding 4) Decryption 5) Secret writing 1) Decoding 2) Decompression 3) Decryption 
Decipherment is the analysis of documents written in ancient languages, where the language is unknown, or knowledge of the language has been lost. It is closely related to cryptanalysis — the difference being that the original document was deliberately written to be difficult to interpret. The term has also been used to describe the analysis of ...
• (n.) The act of deciphering.
De·ci'pher·ment noun The act of deciphering. 
working out what something (often a language) means.