From Srila Prabhupada's lecture on Srimad-Bhagavatam 5.5.1 — October 22, 1976, Vrndavana

Puja means I call you and offer you some respectable [indistinct], some foodstuff, and then very much seated very comfortably. Naturally I may ask, "What do you want?" Then I'll expect, "Give me this. Give me that. Give me that." That is going on. That is called puja. But those who are worshiping the Supreme Personality of Godhead, that is not called puja; that is called seva, krsna-seva. We never say krsna-puja. Nobody… Never says like that. Seva. Seva means it is my duty. I am eternal servant of Krsna. Seva is my duty. So there is difference between puja and seva. Puja means I flatter you to satisfy you, and after being satisfied, you may offer me something, or I'll ask you something and you offer me. That is called puja. That is devata-puja. But, so when you come to Krsna, or Visnu, that is not puja; that is seva. Seva. So as Krsna is offered seva, service, similarly His representative, he is also offered seva.

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Srila Prabhupada writes in the purport to BG 6.47:

The word bhajate is significant here. Bhajate has its root in the verb bhaj, which is used when there is need of service. The English word "worship" cannot be used in the same sense as bhaj. Worship means to adore, or to show respect and honor to the worthy one. But service with love and faith is especially meant for the Supreme Personality of Godhead. One can avoid worshiping a respectable man or a demigod and may be called discourteous, but one cannot avoid serving the Supreme Lord without being thoroughly condemned.

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However we use the word "puja (worship)" in relation to guru. Guru-puja, Vyasa-puja etc. Also Krsna says to Uddhava: mad-bhakta-pujabhyadhika. What is a context in these cases where the word "puja" is used?