siz·able or size·able 
/ˈsaɪzəbəl/ adjective
/ˈsaɪzəbəl/ adjective : fairly large
▪ a sizable contribution/donation ▪ a sizable portion/percentage/proportion of the population ▪ He won by a sizable margin.
▪ a sizable contribution/donation ▪ a sizable portion/percentage/proportion of the population ▪ He won by a sizable margin.
— siz·ably /ˈsaɪzəbli/ adverb, chiefly US
▪ Costs have increased sizably.
/ˈsaɪzəbli/ adverb, chiefly US ▪ Costs have increased sizably.
