Oxicoco vs. arando
While both oxicoco and arando refer to the fruit known in English as "cranberry", the distinction is primarily regional. Arando is the standard term used in European Portuguese (Portugal), whereas oxicoco is the formal dictionary term in Brazilian Portuguese, though it is often replaced by the English loanword "cranberry" in daily Brazilian speech.
Oxicoco
C1This word is the direct translation of cranberry in Brazilian Portuguese and is often used in scientific, botanical, or formal contexts. While it is the correct Portuguese word in Brazil, many Brazilians simply use the English word "cranberry" for commercial products.
O suco de oxicoco é muito recomendado para tratar infecções urinárias.
(Cranberry juice is highly recommended to treat urinary infections.)
Os cientistas estudaram o cultivo de oxicoco em solos ácidos.
(The scientists studied cranberry cultivation in acidic soils.)
Você pode comprar cápsulas de oxicoco na farmácia de manipulação.
(You can buy cranberry capsules at the compounding pharmacy.)
Esta barra de cereal contém pedaços de oxicoco seco.
(This cereal bar contains pieces of dried cranberry.)
O nome científico da planta do oxicoco é Vaccinium macrocarpon.
(The scientific name of the cranberry plant is Vaccinium macrocarpon.)
Arando
B2This is the primary term used in European Portuguese. While arando can refer to the genus generally (sometimes requiring the clarification arando vermelho to distinguish it from blueberries, known as arando azul), it is the common everyday word for cranberry in Portugal.
Em Portugal, o molho de arando é servido frequentemente com pratos de carne.
(In Portugal, cranberry sauce is frequently served with meat dishes.)
Nós colhemos o arando vermelho durante o outono.
(We verify harvest the red cranberry during the autumn.)
Ela fez um bolo delicioso com arando fresco.
(She made a delicious cake with fresh cranberry.)
O chá de arando é popular pelas suas propriedades antioxidantes.
(Cranberry tea is popular for its antioxidant properties.)
Prefiro comprar arando desidratado para colocar no iogurte.
(I prefer to buy dried cranberry to put in my yogurt.)
Summary
In short, use arando if you are speaking typical European Portuguese. Use oxicoco if you are writing formally or scientifically in Brazilian Portuguese, noting that in casual conversation, Brazilians often just say "cranberry".