What's the difference between an English learner's Dictionary and a regular English Dictionary?

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The main difference between English learner's Dictionaries and regular English Dictionaries is that the first one is intended for non-native speakers of English, and the second one is intended for native speakers.

But practically speaking, Let's compare the Merriam-Webster's Learner's Dictionary and the Merriam-Webster Dictionary by Merriam-Webster:

1.) More word entries at Merriam-Webster Dictionary
Merriam-Webster Dictionary includes entries for many words that are not included at Merriam-Webster's Learner's Dictionary because they are rarely used and not essential for learners, such as demulcent and nepenthe.

2.) Definitions are simpler at Merriam-Webster's Learner's Dictionary
The definitions at Merriam-Webster's Learner's Dictionary are shorter and are written in simpler and clearer language, so that non-native speakers of English can understand them. They focus on the most important meanings of a word, and leave out meanings that are rare or unusual. Compare the two definitions for constructive, below, and you will see the difference:

Merriam-Webster's Learner's Dictionary

constructive (adjective)
: helping to develop or improve something : helpful to someone instead of upsetting and negative

Merriam-Webster Dictionary

constructive (adjective)
1: declared such by judicial construction or interpretation
2: of or relating to construction or creation
3: promoting improvement or development

3.) More example sentences at Merriam-Webster's Learner's Dictionary
Merriam-Webster's Learner's Dictionary entries include more example sentences and phrases, highlighted in blue, to show how a word is used. These example sentences were chosen to illustrate typical uses of the word, and they include common phrases, which are shown in bold. See the excerpt from the entry for behavior, below, for an example.

Merriam-Webster's Learner's Dictionary

behavior (noun)
1 : the way a person or animal acts or behaves [noncount] ▪ I'm surprised by her bad behavior toward her friends. ▪ Students will be rewarded for good behavior. ▪ scientists studying the behavior of elephants ▪ normal adolescent behavior ▪ criminal behavior ▪ an interesting pattern of behavior = an interesting behavior pattern ▪ The children were all on their best behavior [=were all behaving very well and politely] at the museum.

4.) Merriam-Webster's Learner's Dictionary includes 22,000 phrasal verbs and idioms
In Merriam-Webster's Learner's Dictionary, the phrasal verbs and idioms associated with a word are included in the entry, giving learners access to information that typical dictionaries do not provide. There are 22,000 idioms and phrasal verbs presented in all. Here are some examples from the entry for the verb shake:

more than you can shake a stick at
chiefly US, informal : more than you can count

shake up [phrasal verb]
1. shake (someone) up or shake up (someone) : to upset (someone) : to shock or frighten (someone)

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