)Historically, many Indo-European languages have expanded the range of their 'weak' inflections, and Esperanto has merely taken this development closer to its logical conclusion, with the only remaining ablaut being frozen in a few sets of semantically related roots such as "pli", "plej", "plu" (more, most, further), "tre", "tro" (very, too much), and in the verbal morphemes "‑as", "‑anta", "‑ata"; "‑is", "‑inta", "‑ita"; "‑os", "‑onta", "‑ota"; and "‑us".