An adjunct is a word or group of words that gives extra information to a sentence; but, when removed makes no harm to its grammar.
I will call you at least by tomorrow
I have almost completely
forgotten to take my passport.
We played soccer in our school garden
"in our school garden" is the first adjunct.
"on Wednesday" is the second adjunct.
Clause vs Phrase vs Sentence
An adjunct can be classified into three groups:
As a Single Word
I saw Ted yesterday
We will have to use the stairs as the lift will be out of order tomorrow
As a Phrase
I usually review vocabulary in the evenings
In the afternoons
, we have a tea break.
I brush my teeth every morning
As a Clause
We finished our assignments before we went out
When the president arrived
, the meeting had already started.