jammern
to whine
To complain in a self-pitying and plaintive way about (often minor) problems or inconveniences; to whine.
Hör auf zu jammern, so schlimm ist die Erkältung nun auch wieder nicht!
Stop whining; the cold really isn’t that bad!

to whine / lament
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to whine
To complain in a self-pitying and plaintive way about (often minor) problems or inconveniences; to whine.
Hör auf zu jammern, so schlimm ist die Erkältung nun auch wieder nicht!
Stop whining; the cold really isn’t that bad!

When you want to state the reason for the whining or lamenting, you usually use the preposition 'über' followed by the accusative. You complain about something: 'über etwas jammern'.
Er jammert ständig über seine Arbeit.
He is constantly whining about his work.
The meaning of 'jammern' (to whine/lament) depends heavily on the context. If it is about small, everyday problems, it means to complain in a self-pitying way. In a context of great misfortune or pain, it means to lament loudly.
Er jammert, weil der Kaffee kalt ist.
He is whining because the coffee is cold.
In the meaning 'sich beschweren' (to complain), 'jammern' (to whine) has a negative connotation. It implies that the person complaining is self-pitying and exaggerating. A typical command is the imperative 'Jammer nicht!' (Don’t whine!).
Jammer nicht wegen des bisschen Regens!
Don’t whine about a little bit of rain!
To express the cause of deep pain or grief, the preposition 'vor' with the dative is often used. Typical combinations are 'vor Schmerz jammern' (to lament in pain) or 'vor Trauer jammern' (to lament with grief).
Der Verletzte jammerte vor Schmerz.
The injured man lamented in pain.
to cry
'weinen' and 'jammern' can both show that someone is feeling bad. 'weinen' mainly means that tears come, for example from sadness, pain, or joy. 'jammern' is more about someone speaking plaintively about a problem or complaining. Tears do not necessarily have to flow. The words can be confused because 'weinen' can also colloquially mean 'to complain' or 'to whine'. In normal usage, however, the important point is: with 'weinen', the focus is on tears; with 'jammern', the focus is on lamenting or complaining.

Herr Krüger jammert am Wochenende über seinen langsamen Computer.
On the weekend, Mr. Krüger complains about his slow computer.
Nach der schlechten Nachricht musste sie lange weinen.
After the bad news, she had to cry for a long time.