Why is there no "it is" between "because" and "easily"?

this is almost like headline-speak, where certain words are omitted for brevity. this really isn't a "normal" way to write. you're correct that if you were to use these phrases in a normal English sentence, it would sound more like this: The vase needs special treatment especially because it is easily damaged.

That's a normal way of writing dictionary definitions.

It's not written as a complete sentence. It's in note form.

Because this is a dictionary definition, there is no subject/object in the sentence; the definition is listed on its own without a subject/object to refer to. Secondly, the implied subject/object could be singular "it" or multiple "they" or could be a pronoun referring to a person "he/she/they", so the dictionary cannot use "it" as it would imply the definition only exists for that case. It is left open for that reason. Third, there are two different clauses in the definition that apply to the implied subject/object. If what's being described is an "it", the sentence would "it is 1. needing careful treatment, especially because it is 2. easily damaged." Once again, the "it" cannot appear in dictionary definitions because the definition has to apply in any sentence it's used in.

That's a dictionary example with a clarification in parentheses. The full sentence is "Molly's health has always been delicate." The part in parentheses is explaining what the word "delicate" means in that context.  Edit: I didn't realize that more than one sentence featured the word "easily"

Since no-one has quite explained it like this, I’d point out that this does seem to be grammatical when read as an adjectival phrase. It’s basically just one long adjective, composed of several words, rather than being a sentence. This makes sense as it’s literally an alternative way of expressing the one-word adjective it describes. Regardless, as others have said, this is how dictionary definitions are written

"it is" would be confusing in this context because there's no antecedent (What does "it" refer to?). Because this is a definition, it's not referring to anything specific.

Dictionaries and headlines are often written only using content words, words that specifically contribute to meaning outside of merely grammatical information.

Dictionary definitions are generally stripped of parts that give them specific person. To put it simply, it's not only "it is" but also "she is", "you are", "I am", "George and Mary are", etc. etc.

It’s because the word « meaning », or the colon, is omitted but implied due to the fact that this is a dictionary definition. If you add them back in and then read the phrase as if you are giving someone the definition, it looks like this: -**delicate;** meaning « needing careful treatment, especially because easily damaged » -**delicate:** needing careful treatment, especially because easily damaged

Dictionary entries are often given in an abbreviated form, because dictionaries were very large books and space was at a premium. This convention has been retained in online dictionaries despite the constraint that produced it no longer applying.

Brevity and wider applicability. It's shorter, quicker to read, and makes sense in more situations e.g. if someone's feelings are delicate you would use "they are delicate" not "it is delicate".

It might be an error, and it might be "headline speak" as others have noted, but it raises an interesting question. Living in the US, I have noticed a trend in the last decade or so for speakers to leave out forms of "to be" where the context is otherwise clear. For example, "that plant needs watered" or "that car needs washed". The bold type example in OP's original question could well fall into this category.

I would also say it's because delicate could also apply to a person, and a person isn't an it, so you would leave the "it is" out so the definition applies to things and people.

Sometimes called “telegraphic” language in memory of actual telegrams. Every unnecessary word would be left out, because the telegraph company charged money (a lot!) for each word. The dictionary is trying to be as concise as possible without loss of meaning. Fine points of grammar are abandoned, but a dictionary is not a grammar book. Interestingly, ignoring the usual rules can improve comprehension. “Hey everybody, there’s a fire here. We should leave the building and call the fire department immediately” is much more difficult to process than “FIRE!!!!”

Everyone here is saying it’s abbreviated, but this isn’t a regular abbreviation even in the context. The actual answer is that “because” can *very occasionally* (usually in older writing) take an adjective phrase: “the hallway would not admit their baggage, because too narrow”, or as in this example. It’s an extremely rare usage and most English speakers will not recognise it as such.

What would the "it" be? The sentence doesn't refer to anything specifically

It's because there is no definition of what they are talking about. So the inserted words could be "it is" or "they are" etc.

It's not really relevant so much for digital documents, but when they used to print dictionaries on paper, this saved space. So it's a holdover from that. They do the same thing with newspaper headlines; it's called "Headlinese".

You’re right. That’s incorrect.

There’s no antecedent for “it”.

Because it represents the meaning of delicate. It is delicate - it is easily damaged. Delicate - easily damaged.

Yeah that seems like an error, both especially and because don't need to be there.

That is simply an error. You’re correct; it should be “because it is easily damaged.”