During takeoff, the Angle of Attack (AoA) is often 11° or more. Is the
11° AoA measured in relation to the chord line of the wing, so that
the pitch attitude at takeoff is 11 - 6 = 5 degrees?
It seems odd that a pilot would know his plane's angle-of-attack in a given situation, but not know what the angle-of-attack was defined to mean. It sounds like you are saying you know the angle-of-attack is 11 degrees during takeoff, but you are not sure whether the pitch attitude is 11 - 6 = 5 degrees, or whether the pitch attitude is simply 11 degrees, or something else.
Setting aside the fact that it seems more likely that you would know the pitch attitude and not the angle-of-attack rather than vice versa, the answer to your question is --
In the world of practical piloting, flight-training guides, etc, angle-of-attack is usually defined to mean the angle between the wing's mean chord line and the free-stream airflow or "relative wind", which is equal and opposite to the direction of the flight path. At the instant of take-off, the flight path is still horizontal. (Take-off may be defined as the point where the flight path begins to curve upwards into a climb.) So if the angle-of-attack is 11 degrees at this instant, and the angle-of-incidence (as usually defined in practical aviation, especially in the American context) is 6 degrees, then the pitch attitude of the fuselage would be 11 - 6 = 5 degrees.
When we are talking about a whole aircraft rather than just a part such as just the wing or just the fuselage, then sometimes angle-of-attack is used to mean the angle of the longitudinal axis of the fuselage to the relative wind, in which case at the instant of takeoff in the example above, if the angle-of-attack were stated to be 11 degrees, then the pitch attitude of the fuselage would also be 11 degrees. But this is not the norm, especially in the world of practical piloting. Normally angle-of-attack is defined as the angle between the mean chord line of the wing and the relative wind.
When angle-of-attack is defined as the angle between the mean chord line of the wing and the relative wind, a pilot usually does not know his actual angle-of-attack at any given instant, unless he does the math by adding the angle-of-incidence (if known) to the pitch attitude (as visually estimated or as read off the attitude indicator), which is why your question seems a bit odd. Still, even the exact angle-of-attack may not be known at any given instant, all pilots should understand that it is extremely important to the flight dynamics of an aircraft at any given instant. Hence it is entirely logical and normal to talk of "increasing the angle-of-attack to maintain altitude in a turn", etc.
To a first approximation, for any given trim setting, the fore-and-aft position of the control stick or yoke serves to control angle-of-attack rather than pitch attitude. The resulting pitch attitude will be strongly dependent upon climb or descent angle, which is strongly dependent on power setting. In a sense the fore-and-aft position of the control stick or yoke actually serves as an "angle-of-attack gauge", though this effect is distorted by many different factors such as the curvature of the relative wind in turning flight, propwash effects, "bending" of the airflow over the tail by deflected flaps, etc. Still, the basic connection between the fore-and-aft position of the control yoke or stick and the angle-of-attack of the wing is one of the reasons for the frequent references to angle-of-attack by pilots, pilot training manuals, etc.
If you are talking to people who aren't Americans, you should know that there is a British usage of the phrase "angle of incidence" that means the same thing as "angle of attack", rather than meaning the angle between the mean chord line of the wing and the longitudinal axis of the fuselage. You'd more likely encounter this usage in an aerodynamics textbook or a design textbook than in a study guide for a private pilot ground school or written test.
Many other definitions of angle-of-attack exist. For example one might measure between the mean chord line of the wing and the local airflow, including the effect of the upwash coming into the wing, and any propwash that is may be present. One can speak of the angle-of-attack of the vertical fin, or the horizontal tail, in which case again one might be measuring relative to the local airflow rather than the free-stream airflow. Even if one is not considering the deflection of the local airflow by the physical presence of the aircraft, one may, or may not, be taking into account that even the undisturbed free-stream airflow or relative wind is "curved" in turning flight to follow the curvature of the flight path. In other words the rotation of the aircraft about its axes creates an additional velocity component in the undisturbed free-stream airflow which differs at different points along the length of the aircraft, and effectively makes the relative wind "bend" to follow the curving flight path. So, it's complicated. But taking the simple case of linear flight, a good starting point for practical piloting is to take the "angle-of-attack" as meaning the angle between the flight path and the mean chord line of the wing.
Useful related external links--
https://www.av8n.com/how/htm/aoa.html#sec-def-aoa
https://www.av8n.com/how/htm/aoa.html#sec-raoa-aaoa
https://www.av8n.com/how/htm/aoa.html#sec-incidence
Some related ASE questions and answers--
(Q) What is the difference between Angle of Incidence (AoI) and Angle of Attack (AoA)?
(A) What is the difference between Angle of Incidence (AoI) and Angle of Attack (AoA)?
(Q) How common is it in current British usage for the angle between the chord line of a wing and the flight path to be called the "angle of incidence"?
(A) How common is it in current British usage for the angle between the chord line of a wing and the flight path to be called the "angle of incidence"?
(Q) Is there a standard word or phrase in the English-speaking world to describe the angle between the fuselage and the flight path / relative wind?
(A) Is there a standard word or phrase in the English-speaking world to describe the angle between the fuselage and the flight path / relative wind? -- (possibly a non-standard view on the matter)
