The names of numbers in the upper teens and the twenties were originally written as three words (e.g. " ", " y "), but nowadays they have come to be spelled predominantly as a single word (e.g. ', '). For the numbers from 21 to 29, the "fused" forms emerged over the second half of the 19th century. For those from 16 to 19, the one-word forms took the lead in the 1940s. Fusing of number-names above 30 (e.g. ', ') is rare.