-xión

Spanish

-xión f (noun-forming suffix, plural -xiones)

Used only in anexión, conexión (and derived nouns), crucifixión, complexión and flexión (and derived nouns)
Although etymologically related, through a detergent brand, Spanish words axión and acción are unrelated in meaning and context, and, in Spain, first word is pronounced using a voiceless alveolar fricative (s), while second one is pronounced using a voiceless dental fricative consonant (θ) for its second "c" (rest of Spanish speakers use "s" for both).