Which suffix signifies the act of cutting into an organ or tissue?

The suffix that signifies the act of cutting into an organ or tissue is "-otomy". This term is derived from the Greek word "tomia", which means "to cut". In medical terminology, "-otomy" is used to describe surgical procedures where an incision is made in order to access the interior of a body part. For example, a laparotomy is a surgical procedure involving an incision into the abdominal cavity.

The other suffix options do not relate specifically to cutting into organs or tissues. The suffix "-ology" pertains to the study of a subject, as seen in terms like "biology", which refers to the study of life. The suffix "-osis" refers to a condition, particularly an abnormal condition or disease, such as "neurosis". Lastly, the suffix "-plasty" indicates surgical repair or reconstruction, as seen in "rhinoplasty", which is a procedure to reshape the nose. Each of these suffixes has a distinct meaning and context within medical terminology, but only "-otomy" directly relates to the act of cutting into tissue or organs.