The past tense form /sæŋ/ is treated as an alternant of /siŋ/. The meaning-difference is considered as expressed by a zero suffix. By this procedure an overt distinction - the replacement of /i/ by /æ/ - is treated as meaningless, while the covert distinction becomes meaning-carrier. [...] it appears to me as strikingly contradictory to treat overt distinctions as meaningless and covert distinctions as meaningful.
- Nida (1948), a pag.415