Compatibleness is defined as the quality or state of being compatible or suitable for something. There are several synonyms that can be used in place of compatibleness, including harmony, agreement, conformity, consistency, concordance, congruity, and coherence. All of these words convey the idea of things being compatible with each other, and working well together. The choice of which word to use may depend on the context and tone of the writing. For example, if the focus is on the agreement between two parties, the word "harmony" may be more appropriate. Similarly, if the focus is on consistency, the word "conformity" may be a better fit.