Simple Definition:

Leukaemia is a type of cancer that affects the blood cells, specifically the white blood cells. Leukaemia prevents the body from making enough healthy white blood cells, which can lead to symptoms such as fatigue [constant exhaustion], frequent infections [disease cause by bacteria or viruses], and easy bruising [when the skin gets injured and turns purple or black].

Example 1: Sarah was diagnosed with leukaemia after experiencing extreme fatigue and getting sick frequently.

Example 2: John noticed he was bruising easily and went to the doctor, who confirmed he had leukaemia.

Very Simple Definition:

Leukaemia is a type of cancer that affects the blood cells, specifically the white blood cells. Leukaemia can make you tired, get sick often, and get bruises easily.

Example 1: Sarah was very tired all the time and kept getting sick. She found out she had leukaemia.

Example 2: John had lots of bruises on his body without remembering getting hurt. The doctor said he has leukaemia.