-ende forms many (but far from all) ordinal numbers, and sju means "seven" and tjue means "twenty", which means that sjuende means "seventh" and tjuende means "twentieth".

...Now as you might figure from the slightly different spellings, these two words are pronounced slightly differently in more conservative dialects, differing really only in the place of articulation of the first consonant. The distinction between these two sounds is however highly unstable and lost in many younger speakers, myself included, leading these two words to only be distinguishable in context, if that.

The cardinal numbers sju and tjue remain distinguishable by number of syllables, since tjue has a little schwa on the end; however when slurring, or speaking quickly in a noisy environment, this isn't always a reliable distinction, either.

All is not lost, though! For there are still the variant forms syvende for seventh and tyvende for twentieth, from the variant cardinal numbers syv and tyve. These number words can feel kind of stilted for me to use, they come from the Dano-Norwegian of old and can therefore feel a bit old-fashioned outside a few set phrases (like "{til syvende og sist|to seventh and last}"^[equivalent to "at the end of the day"] or "{syvende far i huset|seventh father in the house}"^[an old man, esp. if stubborn; in reference to a fairy tale]).

At the end of the day, though, it's generally better to be clear in one's speech than to avoid using old people words.

My own idiolect also mergers /i/ and /y/ and has completely collapsed the pitch accent system, and also deletes some schwas here and there. These features may be a result of growing up bilingual. These idiosyncrasies of my speech lead me to merge words such as {tidlig|early} and {tydelig|clearly}, {å sykle|to bike} and {å sikle|to drool}, and more problematically I have merged the names of the letters I and Y, which makes it a bit harder to spell things out loud.