Recommendation ITU-T G.870/Y.1352 provides terms, definitions and abbreviations used in optical transport network (OTN) Recommendations. It contains a list of the definitions and abbreviations introduced in Recommendations associated with optical transport networks, and can be considered a companion Recommendation to Recommendations ITU-T G.780/Y.1351 and ITU‑T G.8081/Y.1353. This Recommendation does not include terms specific to the physical layer or synchronization. The goal of this Recommendation is to be a single normative source for terms in this subject area.