▁word ▁. ▁Meanwhile , ▁one - letter ▁words ▁other ▁than ▁the ▁conj unction ▁y — nam ely ▁the ▁pre position ▁a ▁and ▁the ▁conj unction s ▁e ▁( the ▁form ▁of ▁y ▁before ▁an ▁[ i ] ▁sound ), ▁o , ▁and ▁u ▁( form ▁of ▁o ▁before ▁[ o ]) — are ▁generally ▁written ▁with ▁acc ent ▁marks ▁from ▁the ▁mid - 1 7 0 0 s ▁to ▁ 1 9 1 1 . ▁ ▁The ▁acc ent - mark ed ▁inf init ive ▁ ▁begins ▁to ▁out number ▁the ▁un ac cent ed ▁form ▁around ▁ 1 9 2 0 . ▁ ▁Mon os yll ab ic ▁pre ter it ▁verb ▁forms ▁such ▁as ▁ ▁and ▁ ▁were ▁usually ▁written ▁with ▁acc ent ▁marks ▁before ▁the ▁ 1 9 5 0 s . ▁ ▁The ▁names ▁of ▁numbers ▁in ▁the ▁upper ▁te ens ▁and ▁the ▁tw ent ies ▁were ▁originally ▁written ▁as ▁three ▁words ▁( e . g . ▁▁ ▁, ▁ ▁y ▁), ▁but ▁now ad ays ▁they ▁have ▁come ▁to ▁be ▁sp elled ▁pre domin antly ▁as ▁a ▁single ▁word ▁( e . g . ▁, ▁). ▁ ▁For ▁the ▁numbers ▁from ▁ 2 1 ▁to ▁ 2 9 , ▁the ▁" f used " ▁forms ▁emer ged ▁over ▁the ▁second ▁half ▁of ▁the ▁ 1 9 th ▁century . ▁ ▁For ▁those ▁from ▁ 1 6 ▁to ▁ 1 9 , ▁the ▁one - word ▁forms ▁took ▁the ▁lead ▁in ▁the ▁ 1 9 4 0 s .