sameness

(noun) the quality of being alike. Example: "Sameness of purpose kept them together."

(noun) the quality of wearisome constancy, routine, and lack of variety. Synonyms: monotony, humdrum. Examples: "He had never grown accustomed to the monotony of his work." "He was sick of the humdrum of his fellow prisoners." "He hated the sameness of the food the college served."