Experiência vs. experimento
When translating the English word "experiment" into Portuguese, the choice between experiência and experimento depends largely on regional variance between Brazil and Portugal, as well as the level of formality. While both words relate to testing and trials, European Portuguese heavily favors experiência for all contexts. In contrast, Brazilian Portuguese often uses experimento specifically for scientific contexts to distinguish it from the concept of having "life experience."
Experiência
A2In European Portuguese, experiência is the standard word used for a scientific experiment, a test, or a trial. In Brazilian Portuguese, experiência is also used for experiments (especially in school settings or casual speech), but it can be ambiguous because it also defines experience (such as work experience or life events).
Os alunos fizeram uma experiência de química na escola.
(The students did a chemistry experiment at school.)
Nesta experiência, misturamos dois líquidos diferentes.
(In this experiment, we mix two different liquids.)
Fazer uma experiência com animais é proibido neste laboratório.
(Conducting an experiment with animals is prohibited in this laboratory.)
Foi uma experiência culinária que deu errado.
(It was a culinary experiment that went wrong.)
Experimento
B1This word is widely used in Brazilian Portuguese to refer specifically to scientific trials, clinical studies, or formal testing procedures. Using experimento in Brazil clarifies that you are talking about a scientific test rather than a life event. In European Portuguese, experimento exists but is quite rare and often sounds archaic or overly technical; speakers there almost always prefer experiência instead.
O cientista publicou os resultados do experimento na revista.
(The scientist published the results of the experiment in the journal.)
Todo o experimento foi realizado em ambiente controlado.
(The entire experiment was carried out in a controlled environment.)
Este experimento social mostrou como as pessoas reagem sob pressão.
(This social experiment showed how people react under pressure.)
Precisamos repetir o experimento para confirmar os dados.
(We need to repeat the experiment to confirm the data.)
Summary
To summarize, if you are in Portugal, use experiência for almost all situations meant to translate "experiment." If you are in Brazil, use experimento within scientific or formal contexts to be precise, and experiência for casual tests or school activities.