Actinically refers to something relating to or caused by the energy of radiation, especially of the sun. Synonyms for this word could include photochemically, photonic, radiantly, sunward, and irradiant. Additionally, one could use terms like UV radiation, solar energy, or ultraviolet light to describe the effects of actinic radiation. These adjectives and phrases can be utilized to convey the idea of something being exposed to a particular type of radiation coming from the sun or other sources. The use of these synonyms can add depth and clarity to scientific writing and help to create a more precise and accurate description of a phenomenon.