I cannot begin to express how true this is. One of the biggest problems I had in the beginning were the words used. They were unfamiliar and uncomfortable. Even today, some words will hang me up a bit. For example, when I hear the word "purgatory", what comes to mind immediately are my Protestant thoughts regarding purgatory. I believed it was a place between heaven and hell in which a soul was either stuck for all eternity or they'd have to work their way toward heaven out of purgatory. I thought it was someplace that Catholics believed that unbaptized babies would be... forever. This, I knew, was not Biblical... and I didn't know why someone would make this up!
Of course, now I understand it. Catholic understanding:
"All who die in God's grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven" (CCC 1030).
The Bible does reference a "purification":
1 Corinthians 3:14-15
"If the work which any man has built on the foundation survives, he will receive a reward. If any man's work is burned up, he will suffer loss, though he himself will be saved, but only as through fire."
Nothing impure can enter heaven (Rev. 21:27) so it is necessary that we be purified before we enter. This is all purgatory is... a period/place of purification. It may be as short as the blink of an eye or it may take a bit longer. We don't know for sure... but the Bible also mentions a waiting place other than heaven for souls already heaven-bound (1 Peter 3:19-20). This may not be referring directly to purgatory but it does indicate the possibility of a place other than heaven or hell.
But back to my point, the words used are often so different that they would trip me up. Mark Shea has a short list of examples:
Apostolate = Ministry
Venial sin = stumbling
Mortal sin = backsliding
Formation = discipleship
Indulgence = gift of mercy
Temporal punishment = discipline of the Lord
Understanding the differences in terms helps me to see that what Catholics believe is not so far off from what I already believed and this understanding helped to bridge an enormous gap for me.
Along with this is the idea that the phrase "personal relationship with Christ" is not often used in Catholic circles, but this does not mean that Catholics don't have one and, if you define it, many will agree that they DO have a personal relationship with Christ! I've also found that some Catholics get hung up on the "born again" phrase. Of course, if you define born-again, Catholics will say, "Yes, I fit that description!"
At one point, before I was even exploring Catholicism, words like liturgy, mass, eucharist, and homily, also bothered me greatly. They seemed so formal, odd and out of place in today's society.
Eucharist = communion
Mass = church service (loosely)
Liturgy = rites, prayers, ceremonies and sacraments of the church (something missing from my non-denominational background)
In short, I see how careful I have to be when talking with non-Catholic friends and family about Catholicism. Simple words could cause them to seriously misunderstand certain aspects of the faith.