I've always been taught "inerrancy" means free of technical errors, such as grammatical, numerical, etc. "Infallibility" on the other hand means completely true in essence. The Bible is certainly infallible, but is not inerrant.

An example: 2 Samuel 8:4 says David took 700 horsemen from Hadadezer, while when relating the same event, 1 Chronicles 18:4 says he took 7,000. It doesn't change the fact that David took horsemen from Hadadezer (infallibility) and defeated him in battle, but it does reveal a transcriptional error.

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Mason
Member, Redeemer Presbyterian Church (PCA)
New York, NY

"Come now, and let us reason together," says the Lord, "Though your sins are like scarlet, they shall be as white as snow; though they are red like crimson, they shall be as wool." - Isaiah 1:18