stalo

One letter from steel, and one letter from a star. This is the sharpest minimal pair in the chapter. Stalo is a shed for animals. Ŝtalo at 2,215, with the hat, is steel. And stelo at 774 is a star. Three common words, one letter apart in two directions, and the vowel one is the trap that bites in writing while the ŝ one bites in speech. If your hat key is broken and you write sxtalo for steel, the x-system protects you; if you type stalo you have just put the cows in the metal.

Say them apart deliberately. Stalo opens with a plain s and ŝtalo with the sh of shall, and Esperanto never merges the two the way German does before a consonant - a German speaker's instinct to pronounce st- as sht- will turn every stable into steel. This is one of the few places where the alphabet rule about one letter, one sound has real consequences at speed.

What it actually covers. A stalo is the building or the stall where farm animals are kept: horses, cattle, pigs. It is not a house, not a barn for hay - that is a garbejo or fojnejo - and not a kennel. The regular Esperanto way of saying it would be ĉevalejo or bovejo with the -ej- place suffix, and both exist; stalo is the borrowed root that covers all of them at once.