区 ward

By May, this ward may contain as many as 1,000,000 people.

ward ★★★★☆ SUF

SUFFIX meaning 'ward'- for example,

新宿区 (しんじゅくく) Shinjuku ward. (ward is a district of a city)

distinguish ★★★☆☆
区 (ward) + 別 (separate) = 区別 (distinguish)

to make a distinction - to tell one thing from another - 2 synonyms, for instance. or 2 similar-looking kanji

ward office ★★☆☆☆
区 (ward) + 役 (role) + 所 (area / attribute) = 区役所 (ward office)

the government office for your ward- where you get your immigration paperwork and junk.