terminology

51% Attack

A situation where one person or organisation is able to hijack the blockchain by controlling the majority of the computing power, otherwise known as the hash rate. For example, they can interupt mining activity and prevent transactions from being confirmed.

Address

A crypto address is a unique location where you store your coins. You also use the address to send and receive your coins. The address will usually consist of a string of letters and numbers, looking something like this:
0xf2403199E81c816ADFE27e850fAf07a24aC04D45

Airdrop

A giveaway of tokens, usually from a new project as a promotion to early supporters.

Altcoin

All cryptocurrencies which are not Bitcoin are known as altcoins (alternative coins). 

Altseason

A term for when bitcoin dominance falls in the market as investors trend towards altcoins.

AMM

Arbitrage

ASIC Mining

ATH

Bag

Bear Market

Blockchain

Block

Block Reward

Buy the Dip (BTD)

Bull Market

CEX

Cold Storage

Cryptography

Cryptocurrency

DAO

dApps

DCA – Dollar Cost Averaging

Decentralised Finance (DeFi)

DEX

Distributed Ledger

Double Spending

Dust Transaction

DYOR

ECDSA

ERC-20 Token

Fiat

FUD

Fork

Gas