The letter that does not belong in the series H D R YL is "R." The other letters can be seen as initials of colors: H for Hue, D for Dark, Y for Yellow, and L for Light. R does not fit into this color categorization, making it the odd one out.
D
y....all others come just two letters after every vovels..
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern D-YL--D. That is, seven letter words with 1st letter D and 3rd letter Y and 4th letter L and 7th letter D. In alphabetical order, they are: dryland
d
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern -YL-D. That is, five letter words with 2nd letter Y and 3rd letter L and 5th letter D. In alphabetical order, they are: wyled
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern A-YL--D. That is, seven letter words with 1st letter A and 3rd letter Y and 4th letter L and 7th letter D. In alphabetical order, they are: amyloid
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern D-A---YL. That is, eight letter words with 1st letter D and 3rd letter A and 7th letter Y and 8th letter L. In alphabetical order, they are: diacetyl
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern D-A-YL. That is, six letter words with 1st letter D and 3rd letter A and 5th letter Y and 6th letter L. In alphabetical order, they are: diamyl
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern DID---YL. That is, eight letter words with 1st letter D and 2nd letter I and 3rd letter D and 7th letter Y and 8th letter L. In alphabetical order, they are: didactyl
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 4 words with the pattern ---YL---D. That is, nine letter words with 4th letter Y and 5th letter L and 9th letter D. In alphabetical order, they are: alkylated ankylosed butylated ethylated
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern D-E--YL-. That is, eight letter words with 1st letter D and 3rd letter E and 6th letter Y and 7th letter L. In alphabetical order, they are: diethyls
According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern D-M---YL. That is, eight letter words with 1st letter D and 3rd letter M and 7th letter Y and 8th letter L. In alphabetical order, they are: dimethyl