What is worship ['Ibadah]?
the term 'Ibadah in Arabic dictionary means submission and surrender. For example, it is said in Arabic: a submissive camel or a trodden path i.e. a path where people always tread.
It incorporates many definitions as follows:
Sheikh al-Islam ibn Taymiya defined worship as: "It is a comprehensive term that encompasses all what Allah loves of words and deeds whether inward or outward."
Ibn al-Qayim said: "Worship is the utmost degrees of love to Allah while accompanied by complete surrender."
Sheikh ibn Sa'di gave many definitions to the term 'Ibadah including: "love and submission to Allah are the essence and core of worship. The complete love and submission to Allah is the reality of worship. If these two concepts or any of them is missed, it is not considered a true worship. This is because submitting oneself to Allah is the core of worship which cannot be achieved except through a perfect love out of which the love of everything else follows ."
In another definition, Sheikh ibn Sa'di said: "Worship or 'Ibadah is a comprehensive term includes all what Allah loves of beliefs, inward and outward deeds. Doing good deeds or refraining from sins are considered a worship which draws a person closer to Allah. Likewise, a person who abandons sins for Allah's sake also worships his Lord and gets closer to Him."
Here, it is worthy to mention that there are two concepts related to the term worship:
-The verb or the action in itself "to worship".
-The object or the means the draws the worshipper nearer to Allah.
Prayer as an example:
- Performing prayer is an act of worship
-It is also a means to get nearer to Allah.
Based on this, according to the second concept, worship can be defined in accordance with the opinion of ibn Taymiya. According to the first concept, it can be defined in accordance to the second and third definition.
However, the fourth definition of ibn Sa'di incorporates the two concepts.
Moreover, from among the definitions of the term worship is this one which states: "It is the good deeds that a person does willingly for the sake of Allah Almighty with no partner." This definition also includes both concepts.
Difference between 'Ibadah and Tawhid al-'Ibdah [worshipping none but Allah]:
There is an apparent difference between the two concepts: worship is an act in itself through which a worshipper gets closer to Allah while Tawhid al-'Ibadah means to worship none but Allah.
 See al-'Ubudiyya p.38
See al-Kafiya Ash-Shafiya fi al-Intisar by al-Najiya sect p.32
 See al-Haqq al-Wadih al-Mubin pages 59-60
 Cited from Sheikh Adb Ar-Rahman ibn Sa'di and his efforts to clarify the issues of 'Aqida p.162.
 See al-Qawl al-Mufid 'ala KitabAt-Tawhid by Sheikh Mohammed ibn 'Uthaimin vol.1, p.10.
 See 'Ubudiyat al-Ka'inat Li Rab al-'Alamin by Farid At-Toni p.25.