This is the 13607th most frequent Russian word.
недостатка
"Недостатка" means "lack" or "shortage" in English.
In this sentence, the word 'недостатка' refers to the absence of insufficiency in persuasiveness, indicating that his speech was convincing.
В его речи не было недостатка в убедительности.
His speech lacked no persuasiveness.
Here, 'недостатка' is used to describe the lack of a deficit in job opportunities, implying that he has many offers.
Недостатка в предложениях о работе у него нет.
He has no shortage of job offers.
In this instance, 'недостатка' is employed to signify a specific deficiency in knowledge.