Basic Abbreviations and Symbols in Amigurumi

If you're new to amigurumi, you'll probably be overwhelmed by all the different abbreviations used in the patterns.

Here's a quick list of some of the basics few abbreviations that are used in many patterns you can find online or in books:
ch (o) : chain
sc (X) : single crochet
hdc (T) : half double crochet
dc () : double crochet
tc () : triple crochet
sl st (●) : slip stitch
dec () : decrease (1 sc in two stitches)
inc () : increase (2 sc in one stitch)
st - stitch

There are also many others that you will encounter when you're more pro in crochet, but these are the most basic ones. Abbreviations are used in the "wordy" patterns and the symbols (in brackets above) are used in pictorial patterns.

Here's a sample of a "wordy" pattern:
Rnd 1: Ch 2. 6 sc in second ch. from hook.
2 sc in each st. around (12 sts)
Rnd 2: [sc, 2sc in next st.] repeat around (18 sts)
Rnd 3: [2sc, 2sc in next st.] repeat around (24 sts)

...

And here's a sample of a "pictorial" pattern which you'll usually find in Japanese crochet books.

I would suggest that it'll be good to learn both methods of interpreting patterns in case a crocheted item you love a lot is only available in the pattern instructions that you don't understand.