bass, base, cage, dare, ease, eave, fast, gash, hash, iamb, jamb, kale, lame, maim, male, nail, oast, pale, rasp, sail, sate, tail, vale, wail, yams, zaps
canalcaratfatalJapanKansaskaratkayakmacawmadamnavalpaganradarsalad
Some six letter words with the fourth letter U are:abductaboundabruptabsurdaccuseacquitactualadjustalludeallureambushamountampuleannualaroundarousearoundarouseassumeassureastuteauburnaugustautumnbeautybelugabemuseblousecasualclausecloudycolumncrouchdebunkdeducedeductdefusedeludedelugedeluxedemuredeputydiluteeffuseendureengulfenoughensureeunuchexcuseexhumefecundfibulafigureflauntfuturegerundgrouchgroundgrouseimmuneimmureimpugnimpureimputeinduceinductinfuseinjureinsultinsurejaguarjejunejujubekabukikahunalegumeliquidliquorlocustluxurymanualmanurematureminuetminutemisusemodulemutualnaturenebulanoduleobtuseoccultoccupyonrushpenuryperuserebuffrebukereducerefugerefundrefuserefutereputeresultresumereturnritualrobustrotundsalutesecureseducesequelsequinsexualshouldshrunksleuthslouchspousesprucesprungstruckstrungsuburbsuturetenurethoughthrushthrusttraumatroughtroupetubuletumultuncurlundulyunfurlunjustunrulyunsungunsureupturnvacuumvicunavisualvolumeyogurt
soldier
The word "level" fits the criteria of having five letters with the second and fourth letters being the same. This word is considered a palindrome, meaning it reads the same forwards and backwards. Palindromes are interesting linguistic constructs that have symmetry in their letter patterns.
abdomen abysmal
Some six letter words:first and fourth letter is the samesecond and sixth letter being the same:BalboaBeebeeBoobooCanchaCoocooIndignKeckleMuumuuPeopleTantraTeetheTentieTestaeTestee
The words with the form _L_O are also, alto, and oleo/olio.
ACROBATIC that is the word i found in the top of my head(: 9 letters, O for the 4th...helpful? (:
No answer yet, but it probably ends with "ing"
humpback whale
lotus
Forty Love