How to invoke a jenkins pipeline A in another jenkins pipeline B

I have two Jenkins pipelines, let's say pipeline-A and pipeline-B. I want to invoke pipeline-A in pipeline-B. How can I do this?

(pipeline-A is a subset of pipeline-B. Pipeline-A is responsible for doing some routine stuff which can be reused in pipeline-B)

I have installed Jenkins 2.41 on my machine.

A little unclear if you want to invoke another pipeline script or job, so I answer both:

Pipeline script The "load" step will execute the other pipeline script. If you have both scripts in the same directory, you can load it like this:

def pipelineA = load "pipeline_A.groovy"
pipelineA.someMethod()

Other script (pipeline_a.groovy):

def someMethod() {
    //do something
}

return this

Pipeline job

If you are talking about executing another pipeline job, the "build job" step can accomplish this:

build job: '<Project name>', propagate: true, wait: true

propagate: Propagate errors

wait: Wait for completion

If you have paramters on the job, you can add them like this:

build job: '<Project name>', parameters: [[$class: 'StringParameterValue', name: 'param1', value: 'test_param']]

Following solution works for me:

pipeline {
    agent
    {
        node {
                label 'master'
                customWorkspace "${env.JobPath}"
              }
    }

    stages 
    {
        stage('Start') {
            steps {
                sh 'ls'
            }
        }

        stage ('Invoke_pipeline') {
            steps {
                build job: 'pipeline1', parameters: [
                string(name: 'param1', value: "value1")
                ]
            }
        }

        stage('End') {
            steps {
                sh 'ls'
            }
        }
    }
}

Adding link of the official documentation of "Pipeline: Build Step" here: https://jenkins.io/doc/pipeline/steps/pipeline-build-step/

As mentioned by @Matias Snellingen and @Céline Aussourd, in the case of launching a multibranch job you have to specify the branch to build like this :

stage ('Invoke_pipeline') {
    steps {
        build job: 'pipeline1/master', parameters: [
        string(name: 'param1', value: "value1")
        ]
    }
}

In my case it solved the problem.