The surname "Helenius" is a Finnish name, pronounced /hɛlɛnius/ (heh-leh-nee-oos) in IPA phonetic transcription. This spelling follows the Finnish language's rules for phonetically transcribing words. The letter "h" is pronounced soft, like the English "h" in "house." The "e" is pronounced like the English "e" in "set," while "ni" sounds similar to "knee." The final "us" is pronounced as "oos." Overall, "Helenius" follows the common patterns of Finnish words and is fairly easy to pronounce once you understand the rules.