Tone changes meaning. Learn these first.

• ā (1st)high, levelsteady high note — mā 妈 = mother
• á (2nd)risingrises like asking 'huh?' — má 麻 = hemp
• ǎ (3rd)dippingdips low then rises — mǎ 马 = horse
• à (4th)fallingsharp fall like 'No!' — mà 骂 = scold
• a (neutral)light, tonelessshort and soft — ma 吗 = question particle
• mā má mǎ màmother / hemp / horse / scoldsame sound, four tones, four meanings
• 3rd + 3rdfirst becomes 2ndnǐ + hǎo → ní hǎo (tone sandhi)