probably
adv.used to say that something is very likely to happen or be true. You use it when you are almost certain but not one hundred percent sure.
adv.used to indicate a high degree of likelihood or probability. Functions as a modal adverb to qualify the certainty of a statement.
“I will probably stay home tonight.”
“If the weather stays this clear, we will probably reach the mountain summit by noon.”
“The researchers concluded that the unusual data points were probably caused by a minor calibration error in the sensor rather than a new physical phenomenon.”
Typically placed before the main verb but after the first auxiliary verb or the verb 'to be'.
In neutral English, this adverb usually sits in the mid-position (before the verb) rather than at the start of the sentence.
Usage probably one · probably wouldn't · probably won't
From Middle English probably, probabily, equivalent to probable + -ly.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.