Those who seek it cause it to grow,

KNOWLEDGE

Explanation:

• "Those who seek it cause it to grow,"

The more someone actively seeks knowledge, the more they learn and expand their understanding.

• "Those who lack it do not know,"

People who don't have knowledge don't realize what they're missing and may not even understand the importance of seeking it.

• "When brandished, it becomes a sword,"

Knowledge can be a powerful tool, like a sword, helping someone defend or assert themselves in conversation or decision-making.

• "But neglect it, and you will grow bored,"

Without knowledge, life can feel monotonous and uninspiring, leading to boredom and a lack of interest in the world around you.