Helpless means you can do nothing for yourself. Not weak in general, but stuck in this moment with no power to act: a newborn baby, a beetle on its back, you at the window while your car is towed away.
Most of the time it describes a feeling rather than a fact, the feeling of watching a parent get ill and having nothing to offer, or a helpless anger at a system that will not listen. It also attaches to things you cannot control, in helpless laughter, helpless with giggles, helpless tears. The noun is helplessness and the adverb is helplessly, which loves verbs of watching: she watched helplessly from the bank. One trap worth learning now. Helpless is not the opposite of helpful; that word is unhelpful. A helpless person cannot help himself, an unhelpful person will not help you.
1adjectivehelplessUnable to do anything to look after or defend yourself.
“The kittens were still blind and completely helpless.”
synonyms: powerless, defenceless
2adjectivestopUnable to stop or control something.
“She was helpless with laughter and had to sit down on the step.”
Too few real examples of this word to estimate which sense is commonest.
Helpless is English building with English bricks: Old English helplēas, from Proto-Germanic *helpōlausaz, which is simply help plus -less, "without help". The -less ending is an old word for "free of, without", and it makes hundreds of English adjectives the same way. The neighbours built theirs identically, in Dutch hulpeloos, German hilflos, Danish hjælpeløs and Swedish hjälplös.
Proto-Germanic
*helpōlausaz
Old English
*helplēas — helpless
Middle English
helples
English, today
helpless
From Middle English helples, from Old English helplēas (“helpless”) from Proto-Germanic helpōlausaz, equivalent to help + less. Compare Dutch hulpeloos (“helpless”), German hilflos (“helpless”), Danish hjælpeløs (“helpless”) and Swedish hjälplös (“helpless”).
Etymology from Wiktionary, CC BY-SA