This is the 2248th most frequent Portuguese word.
tranquilo
Calm; peaceful; serene.
In this sentence, 'tranquilo' is used as an adjective to denote a state of calmness or lack of agitation.
Tudo vai ficar tranquilo, confie em mim.
Everything will be calm, trust me.
Here, 'tranquila' is used in its feminine form as an adjective describing the subject, reflecting her peaceful demeanor.
Ela parece muito tranquila hoje.
She seems very calm today.
In this usage, 'tranquilo' is an imperative suggestion encouraging the listener to relax or remain calm.