As Christians we tend to speak in Christian jargon. Aren’t we aware that other people don’t talk like that? Or do we think it’s neat to have our own lingo that other people don’t understand? The apostle Paul didn’t think that was a good idea: “So likewise ye, except ye utter by the tongue words easy to be understood, how shall it be known what is spoken? for ye shall speak into the air” (1 Corinthians 14.9).
We are not fulfilling the Great Commission if we try to share the gospel in terms that are only understood by those who are already Christians. Let’s not shrug off the lack of results by saying that people just aren’t interested anymore. The fact is that we speak a language that is foreign to our surrounding culture.
What is sin? What does it mean to be lost? What does it mean to feel convicted of our sin? What is the new birth? These words are all in the Bible, but they do not resonate with the mindset of a great part of the population. We could go into long-winded explanations of such words, but it is often better to tell our own personal experiences, in the simplest and plainest words possible.
Some Christians seem to feel they need to sound impressive when they write about their faith. It will likely come across as pompous, and boring. The opposite extreme – using words that are currently hip, can also turn people off. Sometimes a person will hear a new word, assume he knows what it means and use it in conversation. The effect often isn’t what he anticipated. It is important to know our audience and to be able to relate to them on some common ground.
Slogans should be avoided. One that is often heard in our church circles is “We need the unity of the spirit rather than the spirit of unity.” I believe the intention is to say that we should be truly united in the bond of peace, rather than just agreeing to make nice to each other in public. But that isn’t really what the slogan says. In fact, it really doesn’t say anything at all. There is no grammatical difference in meaning between “unity of the spirit” and “spirit of unity.” The use of slogans can become a substitute for thinking. A good rule of thumb would be that if we can’t explain the slogan in simple, easy to understand terms, we shouldn’t use it.
Flatlander Faith 
A crusty old Norwegian logger put it to me this way, “Speak so we know what you say!”
I would rather have someone tell me that, than have him go away and tell others that he couldn’t make heads nor tails of what I was saying.
This reminds me of when people say “spirit of discernment” rather than what it is, the gift of discerning of spirits.
We hear expressions like that from people around us and it’s so easy to start using the expression ourselves without thinking. I try to avoid that, but I’m not sure I’m always aware when I use terminology that may be exclusive to the people I associate with.