Online Dictionary for kids with Pictures will help you learn about things with pictures. But if you learn about a particular word you might not find
https://kidspicturedictionary.com/
Merriam-Webster will help you by putting the words in alphabetical order and when you click a word it will give you the definition of the word. But it does not have pictures if you want to know what it look like.
Kids Words myth it will give you a subject and then tell you the words about the subject. But it can’t teach you a word if it is not about the subject.
https://kids.wordsmyth.net/we/
Google Docs will pop up some links to online dictionaries. MS Word will have the definition of the word.