wailer / waler / whaler are similar-sounding terms with different meanings (referred to as homophones). To better understand the differences, see below for definitions, pronunciation guides, and example sentences using each term. 👇
wailer: (noun) a mourner who utters long loud high-pitched cries.
waler: NA
whaler: (noun) a seaman who works on a ship that hunts whales. (noun) a ship engaged in whale fishing.
wailer: NA
waler: NA
whaler: w·EY·l·er
(Examples are Wikipedia snippets under the CC ShareAlike 3.0 license. Definitions drawn from WordNet.)